Acknowledgements 5 executive summary




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Table 2.1. Rank of stresses affecting priority conservation targets in the Elkhorn Slough watershed



Stresses - Altered Key Ecological Attributes

Severity

Scope

Overall Stress Rank

Tidal Estuary

Erosion

High

Very High

High

Restriction of flow

High

High

High

Pollution

High

Very High

High

Biological invasions

High

Very High

High

Coastal Prairie/Coastal Scrub

Biological invasions

High

Very High

High

Maritime Chaparral

Altered fire regime

High

Very High

High

Habitat conversion

Very High

High

High

Biological invasions

High

Medium

Medium

Altered adjacent habitat

Medium

High

Medium

Erosion

Medium

Medium

Medium

Riparian

Pollution

High

Very High

High

Altered adjacent habitat

High

High

High

Fluctuation of groundwater levels

High

Very High

High

Freshwater Wetlands

Pollution

High

High

High

Groundwater

Very High

High

High

Altered sediment deposition processes

High

High

High

Biological invasions

High

Very High

High

Altered hydrologic regime

High

High

High

Coast Live Oak/Woodland

Habitat conversion

Very High

Medium

Medium

Biological invasions

High

High

High

Erosion

Medium

Low

Low

Altered adjacent habitat

Medium

Medium

Medium


Table 2.2. Rank of threats (sources of ecological stresses) across six priority conservation targets of the Elkhorn Slough Watershed.



D. Prioritization of Goals and Actions

We identified a comprehensive list of actions appropriate for the Elkhorn Slough NERR. These actions were paired with the aforementioned outputs and spanned research, education, stewardship and land acquisition. Reserve staff then worked to prioritize those actions that could reasonably be approached over the next five years with the resources available.


The prioritization process involved two steps. In the first, we prioritized the Reserve’s long-term goals by scoring each for:

  • Potential for conservation return versus investment,

  • Number of endangered and threatened species within the target,

  • Overall urgency of addressing the target in the near future,

  • The relative importance of ESNERR staff expertise in addressing the target, and

  • Whether staff felt that the target warranted ESNERR involvement because of NERRS mission.

Second, each program lead further prioritized by suggesting which of their program’s actions could be achieved with the resources that program typically can engender.


The final product was a list of actions that will be worked on over the next five years and which are the focus of this management plan. Actions that were not prioritized because of lack of resources (winnowed from the second prioritization process, above) remain of great importance and are included in this management plan in hopes of acquiring additional resources. We will seek additional funding and work with our partners to strategize ways to complete any of the actions remaining from the logic models we developed so that all of the prioritized goals will be accomplished. To do this, we will be embarking on a science-based strategic planning process during the course of this management plan’s timeframe.
E. Strategic Planning and Adaptive Management

The Elkhorn Slough NERR continues its conservation leadership through ongoing strategic planning that updates and populates the conservation planning tools we have developed through this management planning process. For each conservation goal, we have formed working groups that will meet periodically to improve and update the planning that has occurred thus far. For instance, we will develop measurable outcomes/measures of success and work with partners to better understand the other resources that can be expected to help achieve prioritized goals. The workgroups will also examine approaches to address the actual threats to priority conservation targets rather than the more symptomatic stresses. The information generated during these ongoing workgroup meetings will help to inform an adaptive management approach (Walters 1986; Gunderson, Holling et al. 1995) and prepare the Reserve to re-examine its work during the next management plan update.


F. References



Chapter III. ESNERR Goal #1



Protect and Restore Estuarine Habitats in the Watershed
A. Introduction

Estuaries are coastal inlets where the fresh water of rivers and streams mixes with the salty water of the ocean. Estuarine habitats at Elkhorn Slough include productive salt marshes, rich mudflats, and meandering tidal channels and creeks. Dozens of vascular algae and plant species, over 100 fish species, over 135 bird species, and over 550 invertebrate species have been reported from Elkhorn Slough’s estuarine habitats (Caffrey et al. 2002). Many of these are species that have broad aquatic distributions, but some are almost entirely restricted to estuarine or brackish conditions, and therefore of special conservation concern at Elkhorn Slough. These include species such as eelgrass, pickleweed, the native oyster, and the tidewater goby. The relative rarity of estuarine habitats along the Pacific coast makes Elkhorn Slough’s role in supporting species dependent on estuarine habitats all the more essential.


While Elkhorn Slough today still hosts extensive estuarine habitats and diverse species, there is strong evidence that local biodiversity is threatened, and has already undergone significant changes in the past centuries (Caffrey et al. 2002). The modifications which have occurred at Elkhorn Slough are not isolated as they have occurred worldwide as a result of human use. Over the past 150 years, human actions have altered the tidal, freshwater, and sediment processes which are essential to support and sustain Elkhorn Slough’s estuarine habitats. This has led to substantial changes in the extent and distribution of different estuarine habitat types (Figure 3.1). Major threats to estuarine habitats result from increased rates of tidal erosion, marsh drowning, and dikes. The accelerated rate of bank and channel erosion in Elkhorn Slough is causing tidal creeks to deepen and widen reducing functions for estuarine fish, salt marshes to collapse into the channel and die, and soft sediments that provide important habitat for invertebrates to be eroded from channel and mudflat habitats. Increases in the flooding of tidal waters on marshes are causing plants to “drown” in central areas of the marsh. Based on current knowledge, the accelerated rates of tidal erosion and marsh drowning are primarily due to the estuarine mouth modifications. The subsidence of marsh areas, the loss of riverine sediment inputs, and sea level rise may also contribute to marsh drowning because marsh plants are sensitive to changes in both hydrodynamics and elevation. Diking causes tidal marsh loss through the conversion to different habitat types and degradation due to subsidence, loss of tidal connectivity, and decreased water quality conditions. Since the 1870s, approximately 30 percent of the salt marsh has been lost due to the construction of levees to drain wetlands for cattle grazing, railroad and road construction, and the creation of freshwater impoundments for duck hunting (Van Dyke and Wasson 2005). After a harbor was constructed at the mouth of Elkhorn Slough in 1947, 50 percent of the salt marsh was lost due to the marsh drowning and bank erosion and continues today at dramatic rates (Van Dyke and Wasson 2005). Tidal creek, mudflat, and channel habitats are also degraded by tidal erosion, which results in approximately two million cubic feet of sediment being exported from Elkhorn Slough each year. Reserve staff members are leading a large, collaborative effort, the Elkhorn Slough Tidal Wetland Project (TWP), with the assistance of many partners to develop specific recommendations to conserve and restore estuarine habitats and implement them. The first two objectives in this section describe these efforts.
A second major threat to the Slough’s estuarine habitats is biological invasions by non-native species that arrived mostly with non-native cultured oysters and on fouled boat hulls. Over 80 non-native species have been documented in the Slough’s estuarine habitats, and the most common, conspicuous invertebrates encountered on a low tide at Elkhorn Slough are invaders (Wasson et al. 2001). Some of these are having significant effects on native communities. The final three objectives in this section address the threat of invasions.


Figure 1. Changes to tidal habitat composition in Elkhorn Slough from 1913 to 2000 (Van Dyke and Wasson 2005)







Figure 3.1. Changes to tidal habitat composition in Elkhorn Slough from 1870 to 2000 based on map and aerial photograph interpretations (Van Dyke and Wasson 2005).

A third main threat to estuarine habitats at Elkhorn Slough is non-point source pollution, including substantial agricultural run-off. Remarkably high nutrient and pesticide concentrations have been documented in the Slough’s estuarine habitats. Few studies have directly addressed the ecological impacts of pollution at Elkhorn Slough, but based on published studies elsewhere, it is possible that changes in water quality have increased the abundance of nutrient-limited producers (e.g., macroalgae such as sea lettuce) and pollution-tolerant animals, while decreasing the abundance of pollution-intolerant species. This threat is addressed under Goal 6 in Chapter VIII of this plan.


Other possible threats to estuarine habitats at Elkhorn Slough include public access impacts, cattle trampling in marshes, and commercial activities such as a wrecking yard, and the Moss Landing Power Plant that takes in large volumes of water in the Moss Landing Harbor area for its cooling system. The role of these factors on the entire estuarine ecosystem has not been thoroughly characterized, and may be minor relative to the three major threats described above, but Reserve staff continues to track the development and impacts of these potential threats. In the coming decade, however, the majority of Reserve staff efforts with regard to estuarine habitats will be focused on the three strategies described below.
Estuarine Habitats facing Restricted Tidal Circulation

In 1872, the Southern Pacific Railroad was extended through the tidal wetlands of Elkhorn Slough, creating a large levee between marshes and tidal creeks on the east and west sides of the main channel. Local landowners built additional levees and dikes so that the impounded areas could be used for duck ponds (1930s), cattle grazing (1940s-1950s), and roads. By the 1960s, approximately 900 acres (30 percent of all tidal marsh areas) in Elkhorn Slough were isolated from the Slough and converted for human uses through diking and draining. The construction of dikes caused the marsh surface to subside which occurs as a result of several processes including drying out of soils, soil compaction and organic matter decomposition, loss of sediment imported with regular tidal flooding, and changes to water movement and storage (Cahoon et al. 1999). In areas where full or muted tidal flow has been returned to these subsided wetlands, mudflats and lagoons have replaced historic salt marsh because of a decrease in elevation of several feet. As a result of past tidal restriction, restoration projects must address the subsidence of marsh elevations. At the same time, land use and freshwater input changes (i.e. diversion of the Salinas River) have reduced the input of riverine sediments normally entering the Slough and building marsh elevations. In addition, a number of estuarine wetlands are behind water control structures or levees which restrict tidal exchange and can reduce water quality due to hypersalinity.


In 1983, tidal flow was returned to approximately 415 acres of estuarine habitats in Elkhorn Slough, known as the Parsons Slough/South Marsh Complex, through both intentional (tidal restoration) and unintentional (winter storms) means. This area continues to be threatened from accelerated rates of tidal erosion and the loss of marsh elevations from subsidence. The Parsons Slough/South Marsh Complex currently supports mostly mudflat and subtidal habitat. There is an opportunity to restore the original complex network of salt marsh and tidal creeks by manipulating marsh elevations. This area may benefit from the installation of a structure to reduce tidal velocities (i.e. culverts, tide gates, earthen or rock levees, or sill) and sediment additions. Although structures are not a preferred restoration technique due to the high-level of maintenance required over time, the options are limited in this high energy system and all efforts will be made to make them adaptable. If large-scale restoration efforts take place (see strategy 2), long-term activities could include the removal of structures and levees that separate estuarine habitats, but in the short-term, the resulting hydrological change could accelerate tidal marsh loss in the rest of Elkhorn Slough.
A phased approach will be taken to reduce the loss of high quality estuarine habitats, restore estuarine habitats that have been lost and the natural processes that support them. These recommended restoration and enhancement activities will be revised and summarized in detail in the final Elkhorn Slough Tidal Wetland Plan that will be completed and publicly available in 2007.
Estuarine Habitats facing Tidal Erosion and Marsh Drowning

Since 1947, the primary cause of salt marsh loss in Elkhorn Slough has been drowning of the marsh in central areas due to increased tidal inundation and subsidence and tidal (bank and channel) erosion along the edges of marshes. The modification of the Elkhorn Slough mouth for the creation of a harbor permanently fixed a deeper opening to Monterey Bay, and is the main cause of subtidal erosion and more recent marsh loss/conversion. Contributing factors may include the decreases in sediment supply due to the diversion of the Salinas River, dike/levee failure and removal, the presence of the Monterey Canyon directly in line with the Slough’s modified mouth, sea level rise (Cayan et al. 2005), subsidence of marsh areas (could be due to groundwater overdraft, tectonic activities, etc.), wave action, and other biogeochemical processes.


The Elkhorn Slough estuary, containing California’s second largest tract of salt marsh, is currently facing unprecedented rates of tidal wetland loss and degradation. Due to human modifications, the ecosystem has become unbalanced and is experiencing accelerated rates of marsh drowning and tidal erosion. This has resulted in a 50 percent loss of tidal marsh through “drowning” of the vegetation in central areas and bank erosion which causes the marsh to collapse into the channel along the edges. Tidal creeks have eroded deepened and widened approximately five times (from an average width of eight feet to forty feet) reducing habitat use by estuarine fish species. Based on a number of meetings with a science panel over the past two years, there is agreement that the estuary is not in a stable state. In fact, almost two million cubic feet of sediment is exported from the Slough each year through habitat loss and degradation. These trends are predicted to continue in the near future if no management actions are taken.
In order to reduce the rapid tidal salt marsh loss and the loss of sediments from channel and tidal creek habitats, the Reserve will continue to lead the Elkhorn Slough Tidal Wetland Project. In the next few years, we will explore the feasibility of different restoration and conservation alternatives with the help of estuarine modeling, tidal hydrology/geomorphology, and habitat restoration experts. We will conduct targeted research to address the key uncertainties about the mechanisms of marsh loss. We also plan to provide community outreach to through meetings and written materials so that they better understand the complex threats and the possible large-scale conservation and restoration actions that may be proposed. Potential large-scale alternatives could include the modification of the dimensions and/or location of the Elkhorn Slough’s mouth to replicate past conditions and the addition of sediment to marsh areas to address elevation issues.
Elkhorn Slough Biological Invaders

Estuaries are by far the most highly invaded coastal habitat types (Wasson et al. 2005). About 60 non-native invertebrates have been documented at Elkhorn Slough, and they include some of the most common species encountered, such as the European Green Crab and the Japanese Mud Snail (Wasson et al. 2001). There are also common algal, plant, and fish invaders in Slough estuarine habitats. Between the 1930s and 1970s, the majority of these invaders probably arrived with shipments of non-native oysters that were cultured at the Slough. Since then, the main introduction route is via hull-fouling on small boats traveling to Moss Landing Harbor. Most of the species arriving in recent decades first became established in San Francisco Bay (to which they were introduced largely by commercial shipping), then spread via boat traffic as well as natural transport of larvae on currents up and down the coast (Wasson et al. 2001). Marine and estuarine invasions have been shown to cause local extinction of native competitors and prey organisms, alteration of community composition and food webs, change in physical habitat structure, and even alteration of flow of energy and materials through whole ecosystems (Grosholz 2002).


In addition to aquatic invaders, non-native upland species have invaded Slough habitats. More than 30 terrestrial non-native plants have been found in the high marsh in the watershed, and these account for about 15% of cover in this rich, narrow transition zone to the upland (K. Wasson and A. Woolfolk, unpublished data). In some places, non-native species such as poison hemlock and ice plant form a virtual monoculture, accounting for the majority of cover in the marsh upland ecotone.
Once invaders become widespread and abundant, they are extremely difficult, if not impossible, to eradicate. However, rapid responses to some recent invasions have resulted in successful eradication or imminent eradication demonstrating the critical need for monitoring and early detection of invaders (Bax 1999, Culver and Kuris 2000, Miller et al. 2004). Management efforts thus should focus on 1) prevention of new introductions, 2) early detection and eradication of new introductions before establishment and spread, and 3) restoration strategies that help favor dominance by native assemblages rather than established non-natives. The Reserve’s actions fall into these three areas, as described below.
B. ESNERR Objectives & Strategies

The Tidal Wetland Planning (TWP) team consists of staff from the Reserve’s Research, Stewardship, Education, and CTP Programs
Objective 1. Restore and Enhance Estuarine Habitats with Restricted Tidal Flows.

Objective 2. Reduce Erosion in Subtidal Habitats and the Loss and Degradation of Intertidal Habitats.
Strategies (for Objectives 1 & 2):

  1. The TWP Team will complete the Elkhorn Slough Tidal Wetland Plan which outlines restoration strategies for estuarine habitats. In order to accomplish this we will:

    1. hold meetings with partners and experts to develop project goals, objectives, and tasks that will support decisions about management and restoration strategies.

    2. write, revise, and review sections of the Elkhorn Slough Tidal Wetland Plan.

    3. continue to involve a technical advisory group to plan and guide project research and monitoring efforts.




  1. The TWP team will obtain funding and permits and develop designs to implement research, restoration, and monitoring projects recommended in the Elkhorn Slough Tidal Wetland Plan. The Reserve will sustain collaborative efforts for the implementation of estuarine restoration projects. In order to accomplish this we will:

    1. identify lead agencies, obtain funding, and oversee contractors that will complete preliminary restoration designs, model potential results, and obtain permits for restoration projects. Preliminary designs and the permitting process may be completed for smaller-scale projects.

    2. hold meetings with partners and technical experts to guide the development of restoration designs, modeling, research, and monitoring activities.

    3. conduct research studies, restoration pilot projects, and monitoring activities of estuarine habitats. Monitoring projects will include support for the installation of tide stations to evaluate tidal inundation patterns and surface elevation tables (SET) and feldspar soil horizon markers to determine the rates of sediment accumulation/erosion and vertical accretion in tidal wetlands. Research projects include the evaluation of how ecological communities respond to different levels of tidal exchange and a comparison of key ecological indicators as they are affected by potential large-scale restoration projects.

    4. support and oversee contracts for research studies, restoration pilot projects, and monitoring activities of estuarine habitats. Monitoring projects will include the installation of tide stations and surface elevation tables (SET). Projects could also include (depending on funding) studies to evaluate the feasibility of sediment addition strategies, determine marsh sediment characteristics, estimate the overall sediment budget of Elkhorn Slough, investigate the role of macroalgae cover and marsh loss, and evaluate historical habitat and salinity conditions. A technical advisory group will be used to help develop and prioritize research and monitoring goals.

    5. identify and if feasible, begin the implementation of restoration and enhancement activities for tidal habitats owned and managed by the Reserve including North Marsh, Estrada Marsh, South Marsh, and Parsons Slough. Potential actions may include the maintenance or improvement of water control structures to reduce hypersalinity issues, the installation of water control structures to reduce tidal erosion, or the addition of sediment to raise the elevation of subsided wetland areas to support marsh growth.

    6. obtain continued funding for an Elkhorn Slough Tidal Wetland Project Coordinator position and support for the involvement of partners, experts, and stakeholders.

    7. hold meetings to integrate ESNERR program activities.




  1. The TWP team will hold meetings, workshops, generate and disseminate outreach materials, and explore land acquisition to obtain support for estuarine restoration and protection projects. In order to accomplish this we will:

    1. hold meetings with key stakeholders and organizations to describe the estuarine habitat threats from tidal erosion and marsh drowning.




  1. The CTP Staff will hold Coastal Training Program workshops at Elkhorn Slough about tidal restoration efforts that have already been implemented in other parts of the country.




  1. The TWP team will create and disseminate outreach materials (newspaper articles, brochures, etc.) to the general public about threats to estuarine habitats and restoration projects.


Objective 3. Prevent new biological introductions into the Elkhorn Slough
Strategies:

  1. The Research team will continue and expand current efforts to educate the public about the value of native estuarine diversity, and explain measures that can be taken by individuals to prevent invasions. This action will build support for regional prevention policy as well as directly reduce the chance of introductions of non-natives by individuals through mechanisms such as release of live bait or aquarium organisms.




  1. The Research team will collaborate with regional policy development, by supporting various agencies with requests for information and participation in meetings aimed at developing policy (such as ballast water discharge protocols or hull-cleaning protocols) that decrease introductions at a broad geographic scale.


Objective 4. Detect and eradicate new biological introductions into the Elkhorn Slough
Strategies:

  1. The Research team will continue early detection program by continuing to disseminate booklets (available online from www.elkhornslough.org/invader.htm) describing two dozen “least wanted” species that have not yet arrived in Elkhorn Slough, yet are likely to have major ecological impacts if they become established.




  1. The Research team will continue annual rapid assessments of estuarine habitats, surveying for plants, algae and invertebrates in Elkhorn Slough to detect changes in native biodiversity and established non-natives, as well as to detect arrival of new species.




  1. The Research team will support regional partners, especially Monterey Bay National Marine Sanctuary and California Department of Fish and Game, in efforts to develop rapid response protocols that identify in advance methods, funding, permitting, and lead agencies that would be appropriate for eradication of new invaders immediately after detection.


Objective 5. Develop restoration strategies that help favor dominance by native assemblages.
Strategies:

  1. The Research team will encourage and support research predicting success and ecological impacts of key regional invaders, especially by Graduate Research Fellows.




  1. The Research team will develop restoration strategies that favor native over non-native biodiversity. In order to accomplish this we will:

      1. conduct literature surveys, attend workshops, and carry out field experiments to identify the biological and physical conditions that favor native estuarine assemblages, and particularly two former estuarine dominants that are now rare, native oysters and eelgrass.




  1. The Research staff will complete an on-going investigation into the role of tidal restriction and cattle trampling on ecotone invasion by non-native plants, and explore the feasibility of restoration strategies for this fragile zone.


C. References
Bax, N.J. 1999. Eradicating a dreissenid from Australia. Dreissena! 10(3):

1-5.
Caffrey, J.M., M.T. Brown, W.B. Tyler, and M. Silberstein, eds. 2003. Changes in a California Estuary: A Profile of Elkhorn Slough. Moss Landing, CA: Elkhorn Slough Foundation.


Cahoon, D.R., Day, J.W., and Reed, D.J. (1999) The influence of surface and shallow subsurface soil processes on wetland elevation: a synthesis. Current Topics in Wetland Biogeochemistry 3: 72-88.
Cayan, D., P Bromirski, K. Hayhoe, M. Tyree, M. Dettinger, and R. Flick (2005) Projecting Future Sea Level Rise. California Climate Change Center. CEC-500-2005-202-SD.
Culver CS and Kuris AM. 2000. The apparent eradication of a locally established introduced marine pest. Biological Invasions 2:245-253
Grosholz E (2002) Ecological and evolutionary consequences of coastal invasions. Trends in Ecology and Evolution 17:22-26.
Miller AW, Chang AL, Cosentino-Manning N, and G. M Ruiz. 2004. A new record and eradication of the Northern Atlantic alga Ascophyllum nodosum (Phaeophyceae) from San Francisco Bay, California, USA. Journal of Phycology 40: 1028-1031
Van Dyke, E. and K. Wasson. 2005. Historical Ecology of a Central California Estuary: 150 Years of Habitat Change. Estuaries 28(2):173-189.
Wasson K, Zabin CJ, Bedinger L, Diaz MC, Pearse JS (2001) Biological invasions of estuaries without international shipping: the importance of intraregional transport. Biological Conservation 102:143-153.
Wasson K, Fenn K, Pearse J (2005) Habitat differences in marine invasions of central California. Biological Invasions 7:935-948.

Chapter IV. ESNERR Goal #2

Protect and restore the watershed’s key freshwater habitats
A. Introduction

Freshwater wetlands occur where land surfaces are saturated or covered by freshwater for sufficient time that the resulting plant community has adaptations to survive these stressful conditions. In the Elkhorn Slough watershed, freshwater habitats occur as riparian corridors, wet meadows, freshwater marshes, and ponds. Riparian habitats are plant assemblages associated with streambanks. Within the watershed, riparian vegetation is dominated by willow (Salix) and is found primarily along Carneros Creek. Wet meadows occur in areas without standing water, but where soils are seasonally saturated and hydric. They sometimes occur as transitional areas between upland grasslands and freshwater marshes, and commonly include sedge (Carex), oatgrass (Danthonia), hairgrass (Deschampsia), barley (Hordeum), rush (Juncus), buttercup (Ranunculus), and bulrush (Scirpus) (Ratliff 1988). Freshwater marsh refers to emergent vegetation growing in at least semi-permanent shallow freshwater. The most frequently dominant freshwater marsh species are bulrush (Scirpus) and cattail (Typha) (Kramer 1988). Open freshwater ponds also occur in the watershed, and include both natural features, such as Werner Lake and McClusky Slough, artificially created agricultural ponds, and artificial impoundments in former estuarine habitats, including the Reserve’s Rookery Pond and Cattail Swale. Also present, but not as well-documented in the watershed, are freshwater seeps and vernal pools.


Freshwater habitats provide important habitat for diverse communities of plants and animals, including sensitive species such as the Santa Cruz Long-toed Salamander (Ambystoma macrodactylum croceum), California Tiger Salamander (Ambystoma californiense), California Red-legged Frog (Rana draytonii), and the Southwestern Pond Turtle (Actinemys marmorata pallida). Unfortunately, freshwater habitats have experienced significant losses over the last 150 years. A network of shallow lakes and freshwater marshes that once extended from south of the city of Salinas to north of the city of Watsonville was drained in the late 1800s and early 1900s for agriculture (Gordon 1996). A series of small upland ponds just north and south of lower Moro Cojo Slough was converted to agricultural and industrial land (Johnson and Rodgers 1854). Freshwater springs and seeps that were once common along the edges of Elkhorn Slough have been lost since the 1940s, presumably due to lowered groundwater levels resulting from agricultural and domestic pumping (Van Dyke and Wasson 2005).
Some freshwater habitats do remain in the watershed, but most face at least some level of ongoing threat. In many cases, exotic plants invade native plant communities, and introduced fishes and amphibians prey upon threatened and endangered animals. In other cases, ponds, marshes and meadows are affected by excessive agricultural runoff which results in sediment accumulation, increased turbidity, and other pollutants. Furthermore, many of the watershed’s ponds are man-made, created from former salt marshes or seasonal streams, or otherwise excavated to form sediment basins or stock ponds. Presumably the hydroperiod, vegetation, and sediment characteristics of these waterbodies are quite different than the original freshwater wetlands that have been lost. The subsequent changes have influenced the plant and animal assemblages that currently inhabit these sites.
Key Freshwater Habitats

Although many freshwater springs, wet meadows, marshes, and shallow lakes have been lost in north Monterey County over the last 150 years, some of these habitats, either natural or artificial, do persist in the Elkhorn Slough watershed. Today, natural freshwater meadow habitat can be found in on the valley floor of the Elkhorn Slough Foundation’s (ESF) and the Elkhorn Slough National Estuarine Research Reserve’s (Elkhorn Slough NERR) Long Valley and in areas of the ESF’s Porter Ranch. Natural freshwater marsh remains in portions of south Strawberry Marsh, at the confluence of Porter Marsh and Corncob Canyon Creek, in the lowest reaches of Carneros Creek, and in portions of McClusky Slough. Natural ponds remain at McClusky Slough and in a string of ponds extending from Werner Lake to several spots along San Miguel Canyon Road and off San Juan Road. Artificial ponds are scattered throughout the watershed. Often, these were constructed as impoundments in natural drainages, or created from diked salt marsh to form duck hunting ponds. On the Reserve, eighteen plumbed wildlife watering devices (‘guzzlers’) were installed in the 1980s to provide water for a variety of wildlife. Other artificial freshwater ponds on the Reserve include Upper and Lower Cattail Swale, Rookery Ponds 1, 2, and 3, Upper and Lower Barn Ponds, and the Five-fingers Pond. These features provide freshwater habitat, but many rely on piped-in well water, have unnatural hydroperiods, or have been severely degraded by pollution and infilling by accelerated rates of agricultural sediments from some surrounding fields. Altering these systems can shift the community composition of plants, vertebrates, and invertebrates (Wellborn et al. 1996, Relyea and Mills 2001, Knutson et al. 2004, Zedler and Kercher 2004, Whiles and Goldowitz 2005). Thus, although some of these altered habitats may provide critical habitat for rare species, others are actually sinks (habitats where local reproduction is insufficient to balance local mortality) for some native species due to the presence of introduced predators. A clear example of this is the presence of the introduced American Bullfrog (Rana catesbeiana) that occurs throughout the watershed primarily at long-lived or permanent wetlands. This species is known to have significant impacts on native Ranid species (Kiesecker et al. 2001, Kats and Ferrer 2003) and has been observed eating red-legged frogs in the Elkhorn Slough watershed.


Today, remaining freshwater habitats play an important role in maintaining sensitive animal species, providing clean water, and supporting important plant communities. The Agriculture and Land-Based Training Association (ALBA) and ESF are working to restore Carneros Creek. ESF and Elkhorn Slough NERR are actively experimenting with apparently successful management of wet meadows and vernal pools, and artificial ponds on the Elkhorn Slough NERR provide important breeding habitat for California Red-legged Frogs (CRLF) and Santa Cruz Long-toed Salamanders (SCLTS). But, the Reserve’s man-made ponds may not be sustainable over the long term. Most ponds on the Reserve were created from converted salt marsh and transitional wetlands that could be restored to their natural habitat in the future. In the long term, the Elkhorn Slough NERR should collaborate with other organizations and private landowners to restore natural ponds, which still exist in the watershed but need enhancement and restoration to provide adequate habitat for breeding amphibians. Therefore, in order to best support the protection and enhancement of local freshwater habitats in both the short- and long-term, Reserve efforts will focus on 1) stewardship of all Reserve freshwater habitats, 2) watershed partnerships and outreach, and 3) research.
Invasive Species

Invasive species have been a significant factor in the decline of federally listed amphibians (USFWS 2002). Introduced bullfrogs and predatory fish prey on CRLF, SCLTS, and California Tiger Salamanders (USFWS 2002 and 1999). Non-native tiger salamanders (Ambystoma tigrinum), formerly legally used as bait and illegally introduced into Monterey County waterbodies, are a significant threat to the endangered California Tiger Salamander. Non-native tiger salamanders compete with and hybridize with the native species (Riley et al. 2003). Chytrid fungus, a pathogen that researchers suspect is non-native to North America, has been linked to the mortality of many amphibian species worldwide. The chytrid fungus attacks amphibian body parts containing keratin (larval mouth parts, frog skin and nervous system), but its role in CRLF declines is currently unknown. Non-native plants, such as French broom, jubata grass, and eucalyptus have been implicated in the degradation of SCLTS habitat (USFWS 1999), while Cape ivy has been shown to impact wetland flood control functions, and may leach potent alkaloids into nearby water bodies (Cal-IPC 2006). While the exact role of plant invasions in amphibian declines is unknown, exotic weeds can certainly change the structure, function, and diversity of freshwater plant assemblages.


Several other invasive species that threaten freshwater habitats in California have not been found in the Elkhorn Slough watershed yet, but have the potential to spread into the region. These include exotic plants such as water hyacinth and hydrilla, and at least one non-native invertebrate. The New Zealand mud snail is a very small exotic freshwater snail that was first discovered in California in 2000. It has the potential to alter primary production and decrease native invertebrate abundance in freshwater habitats, and it appears to be expanding its range rapidly, primarily through human activities on aquatic gear, including shoes and boats.
A central principle of invasive species management is that small infestations can be eradicated, but large infestations can usually only be controlled. In order to be most effective, Reserve non-native management efforts will focus on 1) prevention of new introductions, 2) early detection and eradication of new introductions before establishment and spread, and 3) exotic species control strategies that help favor dominance by native assemblages.
B. ESNERR Objectives and Strategies

Staff from the Reserve’s Stewardship, Education, and Research Programs are involved in the following objectives and strategies
Objective 1: Maintain and enhance key freshwater habitats on the Elkhorn Slough Reserve.
Strategies:

  1. Maintain guzzlers so that they continue to provide habitat for CRLF, breeding tree frogs, birds, reptiles and mammals. Stewardship staff and volunteers will continue to:

      1. maintain open water using vegetation control

      2. maintain plumbing infrastructure




  1. The Stewardship staff will maintain infrastructure and seasonal water levels in order to promote successful CRLF and SCLTS breeding in the short-term. In order to accomplish this we will:

      1. maintain key structures (canal gates, flashboards, plumbing) at artificial ponds in the short-term

      2. supplement water levels in two artificial, plumbed ponds when necessary for successful CRLF breeding in the short-term. CRLF tadpoles need standing water through August in order to metamorphose into adult frogs. In dry years, Rookery Ponds 2 and 3 may dry down by early summer. When necessary, and until other natural freshwater habitats are restored, subsidize these ponds (using existing irrigation infrastructure) through August.

      3. allow Rookery Ponds 2 and 3 to dry down naturally in September, to kill potentially-present bullfrog tadpoles, which need long-lived or permanent water to successfully metamorphose.


Objective 2: Explore and act upon opportunities for watershed partnerships and outreach.
Strategies:

  1. The Stewardship staff will explore partnerships to restore natural ponds on private lands. If we successfully establish these partnerships, we will then seek funding to pursue restoration of historical freshwater habitat.




  1. Dependent on the addition of the Community Outreach Coordinator, the Education staff will educate public about the importance of maintaining natural ponds on private land. In order to accomplish this we will:

      1. work with local partners, public landowners, private landowners, conservation groups, planning interests, and stakeholders in developing a community outreach plan that will include a component on freshwater ponds.


Objective 3: Conduct research to improve management strategies for local freshwater habitats.
Strategies:

  1. The Research team will create a GIS layer of historical distribution of freshwater and riparian areas.




  1. The Research team will monitor water quality in selected freshwater habitats. In order to accomplish this we will:

      1. continue monthly 24-station water quality monitoring program, which includes local freshwater sites.

      2. post summaries of data annually on the Elkhorn Slough NERR website, and make the database available upon request.




  1. The Research team will investigate the characteristics of freshwater habitats in the watershed, and their use by threatened amphibians. In order to accomplish this we will:

      1. continue annual monitoring of about 40 freshwater habitats in the watershed,

      2. analyze data in order to determine if presence and breeding success of native amphibians is linked to conditions such as hydroperiod, invasive predators, disease, and water quality.



  2. The Research team will support research on amphibian metapopulation dynamics. In order to accomplish this we will:

      1. mentor and provide assistance to a graduate student researcher in her studies of red-legged frog movements and habitat usage. She will also investigate population-level effects of invasive bullfrog presence on survival and behavior of the red-legged frog. This research will provide critical information on CRLF metapopulation dynamics, instrumental for improved management of watershed populations.

      2. collaborate with other interested researchers to study ecology and conservation related questions pertaining to SCLTS and California Tiger Salamanders.


Objective 4: Protect Reserve and key neighboring freshwater habitats from selected invaders.
Strategies:

  1. The Stewardship team will prevent new introductions by taking precautions against spreading exotic species and pathogens (e.g., chytrid fungus) among freshwater sites. In order to accomplish this we will continue to ensure that both Reserve staff and visiting scientists appropriately clean boots and other gear between ponds.



  1. The Stewardship team will detect and eradicate newly introduced exotic species. In order to accomplish this we will:

      1. update Elkhorn Slough NERR’s in-house “least wanted” plant cards to include likely freshwater plant invaders (these cards are separate from the published “Early Detection for Aquatic Invaders” booklet developed by the Reserve’s research program for regional detection of marine and estuarine invaders). These cards identify the California Invasive Plant Council’s (Cal-IPC) high priority weeds that are not yet found on the Reserve but have the potential to spread into the area. Least-wanted cards have helped Reserve stewards detect and rapidly control five new upland weeds since 2000.

      2. distribute “least wanted” cards to staff and volunteers




  1. The Stewardship team will detect and remove bullfrogs from Reserve ponds. In order to accomplish this we will:

      1. conduct annual surveys to determine whether bullfrogs are present at any Reserve ponds

      2. if bullfrogs are found, removal of all individuals will be attempted. If bullfrog tadpoles are discovered in any ponds, the ponds will be allowed to dry by the end of August to ensure the failure of this life stage.




  1. The Stewardship team will develop and implement exotic control strategies that help favor dominance by native assemblages. In order to accomplish this we will:

      1. continue to remove Cal-IPC’s high priority weeds, including cape ivy, French broom, Himalayan blackberry, and jubata grass from freshwater habitats (including the edges of ponds, and in riparian woodlands and wet meadows).

      2. attempt to control a suite of “moderate” priority weeds that we have identified as having severe impacts locally. These include eucalyptus saplings and mature outlying trees, velvet grass, some patches of poison hemlock, and harding grass.

      3. plant, where necessary, native plants in removal areas to prevent re-infestation by non-native plants.

      4. decrease the abundance of non-native fish in Elkhorn Slough NERR ponds and guzzlers when and where practical.



C. References
California Invasive Plant Council (Cal-IPC). 2006. Invasive Plant Inventory. Available online at www.cal-ipc.org.
Gordon, Burton L. 1996. Monterey Bay Area: Natural History and Cultural Imprints. Third Edition. The Boxwood Press, Pacific Grove, CA.
Johnson, W. M., and A. F. Rodgers. 1854. Map of part of the coast of California from Pajaro River southward. US Coast and Geodetic Survey.
Kats, L. B., and R. P. Ferrer. 2003. Alien predators and amphibian declines: review of two decades of science and the transition to conservation. Diversity and Distributions 9:99-110.
Kiesecker, J. M., A. R. Blaustein, and C. L. Miller. 2001. Potential mechanisms underlying the displacement of native red-legged frogs by introduced bullfrogs. Ecology 82:1964-1970.
Knutson, M. G., W. B. Richardson, D. M. Reineke, B. R. Gray, J. R. Parmelee, and S. E. Weick. 2004. Agricultural ponds support amphibian populations. Ecological Applications 14:669-684.
Kramer, Gary. 1988. Fresh Emergent Wetland in Mayer, Kenneth E., and William F. Laudenslayer, Jr. (eds.). A Guide to Wildlife Habitats of California. State of California, Resources Agency, Department of Fish and Game. Sacramento, CA.
Marco, Adolfo, Consuela Quilchano, and Andrew R. Blaustein. 1999. Sensitivity to nitrate and nitrite in pond-breeding amphibians from the pacific northwest, USA. Environmental Toxicology and Chemistry, Vol. 18: 2836–2839,
Ratliff, Raymond D. 1988. Wet Meadow in Mayer, Kenneth E., and William F. Laudenslayer, Jr. (eds.). A Guide to Wildlife Habitats of California. State of California, Resources Agency, Department of Fish and Game. Sacramento, CA.
Relyea, R. A., and N. Mills. 2001. Predator-induced stress makes the pesticide carbaryl more deadly to gray treefrog tadpoles (Hyla versicolor). Proceedings of the National Academy of Sciences of the United States of America 98:2491-2496.

Riley, Seth P. D., H. Bradley Shaffer, S. Randal Voss, and Benjamin M. Fitzpatrick. 2003. Hybridization between a rare, native tiger salamander (Ambystoma californiense) and its introduced congener. Ecological Applications 13: 1263-1275.

U.S. Fish and Wildlife Service. 2002. Recovery Plan for the California Red-legged Frog. U.S. Fish and Wildlife Service, Portland, OR.
U.S. Fish and Wildlife Service. 1999. Draft Revised Recovery Plan for the Santa Cruz Long-toed Salamander. U.S. Fish and Wildlife Service, Portland, OR.
Van Dyke, Eric and Kerstin Wasson. 2005. Historical Ecology of a Central California Estuary: 150 Years of Habitat Change. Estuaries Vol. 28:173–189



Wellborn, G. A., D. K. Skelly, and E. E. Werner. 1996. Mechanisms creating community structure across a freshwater habitat gradient. Annual Review of Ecology and Systematics 27:337-363.


Whiles, M. R., and B. S. Goldowitz. 2005. Macroinvertebrate communities in Central Platte River wetlands: Patterns across a hydrologic gradient. Wetlands 25:462.
Zedler, J. B., and S. Kercher. 2004. Causes and consequences of invasive plants in wetlands: Opportunities, opportunists, and outcomes. Critical Reviews in Plant Sciences 23:431.



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