First Annual Meeting
April 14, 2003

Hubbs Sea World Conference Room
San Diego CA

Abstracts

Emerging Issues in San Francisco Estuary Tidal Wetlands Restoration

Authors: Brown, L.R., U.S. Geological Survey, Placer Hall, 6000 J Street, Sacramento, CA 95819-6129, 96-278-3098, lrbrown@usgs.gov

Abstract: Tidal wetland restoration is a key component of the Ecosystem Restoration Program (ERP) of the CALFED Bay-Delta Program (CALFED). One of the ERP’s many goals is to restore from 12,000 to 20,000 hectares of freshwater tidal marsh habitat in the Sacramento-San Joaquin Delta (Delta). This area represents approximately 30 to 50 percent of the freshwater tidal wetlands lost from the Delta since 1900. The purpose of this and other habitat restoration efforts is to benefit populations of plants and animals, with an emphasis on native species. The ERP assumes that the restoration of tidal marsh habitat will re-establish ecosystem processes that will support increased populations of native species and commercially valuable introduced species. Literature reviews and results from recent and ongoing research indicate that the expected benefits of habitat restoration may not be achieved in all cases because of emerging issues ranging from the effects of invasive species to conflicts with other CALFED program areas, such as water quality. The purpose of this presentation is to review some of these emerging issues and identify areas of uncertainty that can be addressed through scientific research.

Value of coastal wetland habitats to fish feeding and growth: a bioenergetics evaluation.

Authors: Madon, S. P. Pacific Estuarine Research Laboratory, San Diego State University, San Diego, CA 92182-1870. smadon@perl.sdsu.edu PH: 619 594 5809

Abstract: Bioenergetics models explicitly link fish energetic processes to abiotic and biotic environmental factors, and are thus valuable for assessing the effects of estuarine processes and disturbances on fish growth. I developed and used bioenergetics models in conjunction with field and lab studies to: (1) quantify the value of vegetated salt marsh habitats to feeding and growth of the California killifish, Fundulus parvipinnis, and to (2) assess growth dynamics of the California halibut, Paralichthys californicus, in wetlands impacted by mouth closures. Killifish: Field estimates of food consumption show that killifish can approximately double their daily food intake by adding marsh surface foods to their diet. The model predicts that killifish grow from 20-100% faster if they add intertidal marsh surfaces to their subtidal feeding areas. Killifish that hatch early (April-May) experience thermal regimes and periods of marsh access through ontogeny that vary from those hatched late (August-September). These differences in thermal and marsh access experiences between early- and late-hatched fish lead to large differences in growth achieved by the next spawning season. Early-hatched killifish are 35-50% larger than late-hatched individuals at 1 yr. age. Halibut: California halibut use coastal wetlands as juveniles but show ontogenetic differences in their tolerance for varying abiotic conditions within these systems. Lab experiments reveal that small juveniles (< 200 mm TL) are largely tolerant of variable estuarine conditions and can grow over wide ranges of water temperatures and salinities. Large juvenile halibut (> 200 mm TL) have reduced tolerances for these abiotic conditions and increased requirements for larger prey, and thus have to emigrate to open-coast environments to maintain growth and fitness. Estuarine mouth closure, a common phenomenon in many coastal wetlands of southern California, likely poses the greatest risk to large juveniles. Bioenergetic model simulations that incorporate both abiotic (temperature, salinity) and biotic (prey type, prey size and prey density) influences reveal that systems such as Tijuana Estuary which have continuously remained open to tidal flushing since the 1980s, are better for supporting juvenile halibut growth, than those such as Los Penasquitos Lagoon where mouth closures occur frequently.

Authors: Sharon Z. Herzka, Department of Ecology, Center for Scientific Investigation and Higher Education of Ensenada, Baja California, Mexico, PO Box 434844, San Diego, CA 92143. 011-52-646-175-0500 (W), 011-52-646-175-0545 (F), sherzka@cicese.mx

Abstract: Many fish species recruit from coastal areas to estuaries during early life. Within estuarine systems, the use of specific habitats can be stage-specific. Tracking the temporal and spatial migration patterns in nursery areas is important for both management and conservation purposes. The stable isotope ratios of fish tissues integrate the isotopic composition of their food sources, which in turn reflect isotopic signatures that can be related to specific habitat types. Stable isotope ratios can thus be used to infer patterns of recent habitat utilization. Moreover, a change in habitat may result in feeding on an isotopically distinct food web, in which case the isotopic composition of the tissues will gradually shift to reflect the new foods. Stable isotopes can thus serve as natural tracers to identify individual fish that have recently undergone a change in habitat. A stable-isotope based empirical model was developed to estimate the size and time elapsed following a change in habitat preference for individual fish. Its applicability to studies of migration among habitats during the early life of estuarine-dependent marine fishes will be discussed.

Authors: Lenny Grimaldo, Environmental Scientist/Fishery Biologist, Department of Water Resources, 3251 S Street, Sacramento, CA 95816. (916)227-9178 lgrimald@water.ca.gov

Abstract: Our ability to design restoration projects aimed at improving ecosystem conditions for native fishes in the Sacramento-San Joaquin Delta has remained limited by a lack of basic ecology information. We present results from two food web studies that shed light on the trophic dynamics of native and introduced fishes residing in flooded islands of the Delta. We analysed the stable carbon and nitrogen isotope ratios of over 1,300 juvenile fishes and other food web components. Our results showed that, 1) carbon sources assimilated by juvenile fishes differed between species occupying inshore and offshore habitats, and 2) trophic hierarchy among fishes was best described by functional feeding groups. Diet content analyses corroborated the isotope data, showing that juvenile fish prey items were largely comprised of invertebrates found in respective habitats whereas sub-adult fish diets were more diverse, yet still reflective of local prey resources. We conclude that restoration should proceed using our increasing understanding about the relationships between habitats, trophic pathways and fish abundances as criteria for selecting and prioritizing potential sites. We now recognize that not all shallow habitat is equal in form or function, and therefore, expect for fish to vary accordingly based on inherent feeding and rearing strategies.

Authors: Steve Cannata, Associate Fisheries Biologist, California Department of Fish and Game, 1487 Sandy Prairie Court, Fortuna, CA 95540. scannata@dfg.ca.gov

Abstract: Studies of the Navarro and Albion River estuaries were conducted to help determine their roles as juvenile steelhead (Oncorhynchus mykiss) and coho salmon (O. kisutch) habitat. These two estuaries are located less than five miles apart, on the coast of Mendocino County. The study period for the Navarro River estuary was May 20, 1996 to December 3, 1997. The study period for the Albion River estuary was May 22 to December 24, 1997. We used a beach seine (100 X 8 ft. with an 8 X 8 ft. bag, mesh sizes were ½ inch in seine and 3/8 inch in the bag) to sample fish populations at 9-10 sites in each estuary. Samples were collected from one to four times per month at each site. Vertical profiles of water temperature, salinity, conductivity, and dissolved oxygen also were collected at each site.

Fish populations of small coastal lagoons in southern California.

Authors: Camm C. Swift, Presenter. Emeritus, Section of Fishes, Natural History Museum of Los Angeles County. Mailing address: 346 West Leroy Avenue, Arcadia, CA 91007-6909, 626-447-5846, camswift@pacbell.net

Abstract: Coastal lagoons north of Pt. Conception on Vandenberg Air Force Base and southward on Marine Corps Base Camp Pendleton differ in their fish faunas. In both areas barrier sand bars close the lagoons for most of the dry season. Salinities are usually less than 5 ppt. Water temperatures fluctuate minimally paralleling moderated coastal air temperatures. Lagoon temperatures in the north are warmer than the ocean whereas in the south water temperatures are warmer than the ocean in winter and cooler than the ocean in summer. The numerically dominant fish both north and south is the brackish water tidewater goby. In the north lagoons and tributary streams are also nurseries for cool water species, prickly sculpin and starry flounder, and in the south for warm water species, topsmelt, diamond turbot, and striped mullet. Young and juvenile staghorn sculpin recruit to lagoons both north and south. Other common local estuarine species (California killifish, barred pipefish, shiner surfperch, California halibut, arrow goby, mudsucker, cheekspot goby, shadow goby, and the non-native yellowfin goby) are rarely encountered in these non-tidal systems. The El Nino of 1998 provided enough water for several of these rare species to invade these small systems for one or a few years.

What do long-term datasets reveal about the ecology of longfin smelt (Spirinchus thaleichthys) in the San Francisco Bay estuary?

Authors: Jonathan A. Rosenfield; Univ. California Davis, Center for Integrated Watershed Science and Management. jarosenfield@ucdavis.edu. Randall D. Baxter; California Department of Fish and Game, Central Valley Bay Delta Branch

Abstract: Longfin smelt (Spirinchus thaleichthys) are native to the San Francisco Bay estuary, where they are a species of special management concern. Preliminary analyses of several long-term (>20 year) data sets indicate that these fish have seasonal migration patterns that are influenced by annual outflow conditions. These migrations, and their interaction with annual meteorological conditions, complicate estimation of population size and management for preferred conditions. When these intra-estuary migrations are taken into account, several lines of data reveal a long-term decline in this population. The long-term data sets also suggest important aspects of longfin smelt behavior and ecology which may improve the efficacy of future sampling and management of this important population.

The prevalence of nonindigenous species in southern California bays and harbors and their effects on benthic macroinvertebrate communities

Authors: J.A. Ranasinghe, Presenter, SCCWRP, 7171 Fenwick Lane, Westminster, CA, 92683, 714-372-9218, anandar@sccwrp.org; R.G. Velarde, City of San Diego, 4918 N. Harbor Dr., San Diego, CA, 92106, 619-758-2331, rvelarde@sandiego.gov; D.B. Cadien, CSDLAC, P.O. Box 4998, Whittier, CA, 90745, 310-830-2400, dcadien@lacsd.org; T.K. Mikel, ABC Labs, Inc., 29 North Olive St., Ventura, CA, 93001, 805-644-8686, tkmikel@pacbell.net; H. Lee II, U.S. EPA, Western Ecology Division, Newport, OR, 97365, 541-867-5001, lee.henry@epa.gov

Abstract: We assessed the prevalence of nonindigenous species (NIS) in the benthic macrofauna of southern California embayments from 123 samples collected in 1998. NIS were prevalent, occurring in 121 samples. They accounted for only 4.3% of the species but contributed 27.5% of the abundance. In another 1999 West Coast study that excluded San Francisco Bay, NIS were more prevalent in southern California embayments than other areas. NIS occurred at 100%, 33%, 71% and 68% of sampling sites in southern California, northern California, Oregon and Washington, respectively. On average, they contributed 11.9%, 2.8%, 15.1% and 10.8% of the species and 22.7%, 2.6%, 14.1%, and 6.0% of the abundance in each sample. In the southern California study, there were no apparent differences in NIS abundance, proportional abundance or composition among ports servicing ocean-going vessels, small boat marinas, or areas where boats were not moored. NIS abundance in southern California embayments was positively correlated with the abundance and richness of other species; there was no negative impact at this gross level. However, negative effects on specific native taxa cannot be ruled out without further study. The positive correlations are likely related to biogenic structures built by the two most abundant NIS.

Authors: Robert McAdory* and David Mark, Estuarine Engineering Branch, Coastal and Hydraulics Laboratory, US Army Engineer Research and Development Center, Vicksburg, MS, and Jane Grandon, US Army Engineer District, Los Angeles, CA.

*Member of CAERS

Abstract: Cabrillo Beach is a small, popular beach in the southwest corner of the Port of Los Angeles in the San Pedro neighborhood, co-located with the Cabrillo Marine Aquarium. http://www.scc.ca.gov/Wheel/lapage/6_so_la/harbor/cab.html

The beach has water quality problems, particularly e-coli, due in part to the beach's isolated location and the resulting poor circulation of water into and out of its vicinity. The Port constructed the ~ 17 ft deep Cabrillo Shallow Water Habitat (CSWH) along the breakwater between Cabrillo Beach and Angel's Gate to provide habitat and feeding area for fish and marine birds. Determining of the impact of this habitat on water quality at Cabrillo Beach included use of a numerical model for hydrodynamics in the Los Angeles Harbor. Model calculations were performed with and with out the CSWH and with and without a proposed expansion of the CSWH. Results of the calculations showed that very little change in the circulation of the water in the vicinity of Cabrillo Beach. The modeling will be discussed and short videos of the circulation as calculated will be presented.

Authors: Charles Simenstad, School of Aquatic and Fishery Sciences, University of Washington; Denise Reed, Department of Geology and Geophysics, University of New Orleans; Philip Williams, Michele Orr, Philip Williams & Associates, Inc., Stephen Bollens, Romberg Tiburon Center for Environmental Studies, San Francisco State University; Nadav Nur, Pt. Reyes Bird Observatory

Abstract: BREACH II research builds on and expands our initial (BREACH I) CALFED Category III-supported research in the Sacramento-San Joaquin Delta to address the considerable uncertainty in predicting the outcome and ecological benefit of restoring shallow-water tidal habitat in three different regions of the Bay--Delta: the Delta, Suisun Bay, and San Pablo/North Bay. BREACH II studies address both the feasibility of restoration of shallow water habitat, and differences inherent to different regions of the Bay-Delta continuum, as well as evaluate the contribution of that endpoint to the long-term recovery of fisheries and ecological integrity of the Bay-Delta. Goals of the BREACH II investigations are to: (1) systematically address the present status, rates, and patterns of tidal ecosystem restoration in recognizably different Bay-Delta ecosystems; (2) evaluate factors that promote rapid restoration of shallow-water habitat versus factors that have potentially inhibited natural rates and patterns of functional development; (3) evaluate the contribution of shallow water habitats to food webs supporting Bay-Delta ecosystems; and (4) assess the overall outcome of breached-levee restoration in the different Bay-Delta regions and recommend optimum strategies and spatial distribution of future restoration initiatives. The focus of our sampling design and synthesis is a BREACH conceptual model that we have developed for restoration patterns, rates and processes in the Delta. We are expanding from the initial BREACH studies in the Delta to Suisun Bay-San Pablo/North Bay our approach of using the "natural experiment" of the diverse age distribution of selected breached-levee sites in a 'space-for-time substitution' to predict the patterns and rates (trajectories) of restoration that would be expected from levee breaching. As in our initial CALFED studies in the Delta, we are systematically evaluating the rates and patterns of restoration, and determining sources of variability, in both naturally and artificially restored diked wetland sites of a broad spectrum of ages as compared to the reference sites. Our objectives include: (1) Assess hydrological, geomorphological, biogeochemical and ecological indicators at diverse, differently-aged sites of formerly diked wetlands that have reverted to tidal inundation; (2) compare indices of fish and wildlife habitat quality of these naturally breached-dike sites to existing mitigation and restoration sites that were purposefully constructed by dike breaching or comparable restoration actions; and, (3) using the same indicators, compare the status of these restored wetlands to wetland function at natural reference marsh sites. This approach is integrated into a developing conceptual model that relates transitional phases in the development of shallow water habitat to the support of fish and wildlife. Our products are intended to provide critical information necessary to predict whether breached-dike restoration strategies proposed under CALFED would provide natural wetland functions to support tidal (shallow-water) aquatic habitat for other aquatic and terrestrial species of concern and rehabilitate a robust Bay-Delta food web.

Successes and shortcomings in habitat restoration: a case study of Cerithidea californica (Gastropoda) colonization and fitness in a created tidal mudflat

Authors: Anna R. Armitage, Peggy Fong, UCLA Dept. of Organismic Biology, Ecology and Evolution, 621 Charles E. Young Dr. S., Los Angeles, CA 90095-1606. armitag9@ucla.edu

Abstract: Salt marsh restoration often involves re-establishing tidal flow and vascular plant transplantation, and faunal colonization is expected to follow. A four-year study of the colonization and fitness of a common gastropod, Cerithidea californica, in a created southern California tidal mudflat revealed some successes and shortcomings in the development of the created site. Snail densities in the created site were lower than in an adjacent natural site throughout the study period, although the differences between sites decreased in magnitude by the end of the study, suggesting a recovery trajectory. Snails were not evenly distributed throughout the created site due to habitat quality and limited snail dispersal ability. Principal components analysis suggested that environmental factors explained some of the initial variability in adult (48%) density but little of the variability in juvenile density. After four years, up to 79% of the variation in adult snail density was explained by distance from the natural/created site transition zone. Juvenile snails were not related to distance from the transition zone, possibly due to their greater dispersal ability. Snails that did colonize the created site displayed similar fitness as snails in the natural site, as growth rates, mortality rates, and reproductive output were similar between sites. Thus, although C. californica fitness was similar between sites, environmental factors and dispersal limitations restricted snail colonization and suggest that the habitat value of the created site is not yet equivalent to that of the natural site.

Estuarine macroalgae take up nutrients from sediments leading to increased growth and tissue nutrient content

Authors: K. Kamer¹, R. L. Kennison², P. Fong², and K. Schiff^1, kristak@sccwrp.org, ¹Southern California Coastal Water Research Project, Westminster, CA, 92683, ²Department of Organismic Biology, Ecology and Evolution, University of California, Los Angeles, Los Angeles, CA, 90095

Abstract: Bloom-forming macroalgae such as Enteromorpha intestinalis take up nutrients from the water column as well as those fluxing from sediments. We hypothesized that the importance of these sources to E. intestinalis varies along a nutrient resource gradient within an estuary. We tested this by constructing experimental units using water and sediments collected from 3 sites in Upper Newport Bay estuary, California, US, that varied greatly in water column nutrient concentrations. For each site there were three treatments: sediments + water; sediments + water + algae (E. intestinalis); inert sand + water + algae. Water in units was exchanged weekly simulating low turnover characteristic of poorly flushed estuaries. The importance of the water column versus sediments as sources of nutrients to E. intestinalis varied with the magnitude of the different sources. When initial water column DIN and SRP levels were low, estuarine sediments increased E. intestinalis growth and tissue nutrient content. In units from sites where initial water column DIN was high, there was no effect of estuarine sediments on algal growth or tissue N content. However, salinity was low in these units and may have inhibited algal growth. Water column DIN was depleted each week of the experiment. Thus, the water column was a primary source of nutrients to the algae when water column nutrient supply was high, and the sediments supplemented nutrient supply to the algae when water column nutrient sources were low. Depletion of water column DIN in sediment + water units indicated that the sediments acted as a nutrient sink in the absence of algae in this experiment. Previous studies have demonstrated the potential importance of sediments as a source of nutrients to primary producers; our data provide direct experimental evidence that macroalgae utilize and ecologically benefit from nutrients stored in estuarine sediments.

Using macroalgae as an indicator of terrestrial influences in southern California estuaries.

Authors: Risa A. Cohen and Peggy Fong, University of California, Los Angeles

Abstract: The relative importance of terrestrial and marine sources of nutrients to estuaries has long been debated. In northern California it has been shown that ocean sources may dominate, but in southern California the majority of studies have focused on nutrient inputs from watersheds. Our objective was to use Enteromorpha spp., opportunistic macroalgae that respond rapidly to changes in salinity and nutrient availability, to obtain integrated measures of freshwater input, nutrient supply and nutrient source in estuarine areas. We outplanted cultured algae in the field along salinity gradients in three southern California estuaries, Newport Bay, Mugu Lagoon and Carpinteria Salt Marsh for 24 hours. Algal tissue was then analyzed for potassium content (K⁺) to measure osmoregulatory changes, nitrogen content (total N, NO₃^- and NH₄⁺) to examine changes in nutrient supply and d ¹⁵N to assess nutrient sources. A total of ten stations along the salinity gradient at each estuary were sampled and replication was 5-fold at each station. Experimental cages were anchored in the same locations for assays performed during both wet and dry seasons. Physical measurements of environmental parameters (salinity, water nutrient concentration) were also taken at each station. Although salinity correlated well with tissue K⁺ content for site, season, and estuary, there was little agreement between water N concentration and both tissue N and d ¹⁵N. These findings from the bioassay suggest that the rivers may not be the main sources of nutrients to these estuaries, even during the wet season. Therefore, the amount of nutrients from groundwater and other unidentified sources must also be determined to ensure successful management plans.

Nutrient and Macroalgal Dynamics in 5 Southern California Estuaries

Authors: Rachel L. Kennision¹, Krista Kamer², and Peggy Fong¹ rlk@ucla.edu, ¹Department of Organismic Biology, Ecology and Evolution, University of California, Los Angeles, Los Angeles, CA, 90095, ²Southern California Coastal Water Research Project, Westminster, CA, 92683

Abstract: We investigated seasonal nutrient dynamics and macroalgal community responses in 5 estuaries in southern California that have a wide range of distinct characteristics. Tijuana River National Estuarine Research Reserve, Los Penasquitos Lagoon, Newport Backbay State Ecological Reserve, Mugu Lagoon and Carpinteria Salt Marsh Reserve have been sampled seasonally since December 2001. Three transects were permanently established in each estuary: at the mouth, at the primary freshwater input, and midway between the two. Along each transect we sampled water column salinity, organic and inorganic N and P and dissolved oxygen concentrations; sediment grain size, N and P concentrations, organic content and redox potential; algal species percent cover, biomass, and tissue N and P content. By gathering data along freshwater gradients within estuaries, we can make within-estuary comparisons of nutrient availability and algal biomass as well as between-estuary comparisons. Preliminary results show seasonal patterns for algal biomass with blooms in December and June. For all estuaries combined, water column NO₃ was higher in December than in June, and there was no significant relationship between water column NO₃ and total algal biomass, suggesting that water column NO₃ is not an accurate estimation of available nutrients in the system. These data will be used to determine relationships between nutrient inputs, nutrient availability, macroalgal abundance and dissolved oxygen availability; one of the overall goals of this project is to provide data that will assist in development of nutrient criteria for estuaries by local and regional water quality agencies.

The North versus The South: are nutrient dynamics fundamentally different?

Authors: Peggy Fong, Katharyn E. Boyer, and Anna R. Armitage

Abstract: In general, estuaries in southern CA are smaller, receive less freshwater during a shorter wet season, are less tidally influenced, and have much more developed watersheds than their counterparts to the north. As sources, sinks, and processing of nutrients are all influenced by these factors, it is likely that estuaries in these two regions have fundamentally different nutrient dynamics. Two lines of evidence support this hypothesis. First, ¹⁵N content of algae collected in summer (2000) from estuaries spanning the coast from Tijuana Estuary to Bodega Bay suggests that nutrient sources in northern CA are dominated by upwelled water that advects into the estuary. Within northern estuaries, tissue N content of algae decreases from the ocean to the river as the tidal water is stripped of nutrients. In contrast, in southern CA both ¹⁵N and tissue N content in algae was highest where the river enters the estuary, decreasing as nutrients are removed while water moves down-estuary. Very high ¹⁵N suggests that recycled and groundwater nutrient sources dominate. The second line of evidence, from nutrient limitation experiments, suggests that in summer, both N and P limit algae from estuaries in southern CA while neither nutrient limits algal growth in northern CA. Thus, in summer, recycling and groundwater supplies are not sufficient to meet the nutrient demands of algae in southern CA while upwelling and advection are sufficient in northern CA. This may be related to many factors, including differences in the rates of supply from these sources as well as differences in algal growth and biomass accumulation between these regions.

Historical Changes In Mission Bay And Observed Changes In Benthos

Authors: Jeffrey A. Crooks, Tijuana River National Estuarine Research Reserve, Imperial Beach, CA, Deborah M. Dexter Dept. of Biology, San Diego State University, San Diego, CA.

Abstract: Mission Bay has undergone dramatic changes over the last 150 years. Originally described as a relatively deep water lagoon fringed by extensive marshlands, the bay underwent its first major anthropogenic transformation with the diversion of the San Diego River into the eastern end of the bay in the mid-1800's. This caused much of the Mission Bay to fill with sediments. In the mid-1900's, the river was again diverted, this time bypassing Mission Bay and discharging into the Pacific Ocean via a flood control channel. The bay itself was also dramatically modified, with extensive dredging and filling leaving little natural habitat remaining. This massive habitat alteration, coupled with organic enrichment from urban runoff, overharvesting, and exotic species invasions, have greatly altered biotic assemblages in the bay. The cumulative effects of these stresses can be tracked by examining shifts in bivalve communities over time, although it is difficult to assess the relative magnitude of each. Experimental manipulations, however, can provide some insight into factors causing alterations in benthic community structure. These suggest that the invasion of an exotic mussel, Musculista senhousia, has been important as an agent of change in the bay.

Water Circulation And Transport In Mission Bay

Authors: J. L. Largier, Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA 92093-0209; jlargier@ucsd.edu, M. L. Carter, Scripps Institution of Oceanography, UCSD, D. Sutton, San Diego Supercomputer Center, UCSD, M. Roughan, Scripps Institution of Oceanography, UCSD, J. Helly, San Diego Supercomputer Center, UCSD, P. Atjai, Marine and Environmental Studies Program, University of San Diego, L. Clarke, Scripps Institution of Oceanography, UCSD

Abstract: Mission Bay is characterized by long dry summers with low or zero inflow of freshwater. As in many estuaries in California and other mediterranean-climate regions, the primary exchange of waters between parts of the bay and with the ocean is due to tidal circulation. Model estimates of residence time match well with observed temperature gradients in the outer bay and hypersalinity in the inner bay – ocean water that remains in the shallow bay will become warmer and also increasingly salty due to an evaporative loss of freshwater. This tidal mixing of back-bay waters was quantified through dye release experiments and direct measurements of current velocities over time. In the outer bay, tidal exchange is active and water types are similar to that in the open ocean. In winter, significant freshwater inflow to the inner bay occurs briefly during and immediately following rain events. This results in high turbidity and low salinity in the bay. The resultant stratification leads to enhanced flushing so that low-salinity water exhibits short residence times. However, when the volume of inflow is small the freshwater may mix into the back-bay waters and remain resident for weeks or more.

Plankton Dynamics In Relation To The Physical And Chemical Environment In Mission Bay

Authors: Ronald S. Kaufmann, Marine and Environmental Studies Program, University of San Diego, 5998 Alcala Park, San Diego, CA 92110, kaufmann@sandiego.edu, Ryan B. Griggs, Marine and Environmental Studies Program, University of San Diego, John N. Kittinger, Marine and Environmental Studies Program, University of San Diego, Brandon L. Swope, Marine and Environmental Studies Program, University of San Diego, B. Chris Stransky, Amec Earth and Environmental, San Diego, CA, Hiram A. Sarabia, San Diego BayKeeper, San Diego, CA

Abstract: Mission Bay is a shallow estuary flushed primarily by tidal circulation and surrounded on three sides by the City of San Diego. Three freshwater creeks and over 100 storm drains empty into the bay, carrying chemicals that have the potential to impact plankton communities both positively and negatively. A time series study was initiated in July 2001 to examine temporal and spatial variation in the concentrations of nutrients (nitrate, phosphate, silica) and the dynamics of plankton communities within Mission Bay. Nutrient concentrations in the bay have been relatively low, with considerable seasonal and spatial variation. During the summer, regions near the mouth of the bay have displayed consistently lower temperature, salinity, and concentrations of nutrients compared to more poorly flushed
sites in the eastern portion of the bay. Seasonal variation in phytoplankton populations has followed a classical paradigm, with greater abundances of diatoms in the spring and dinoflagellates in the summer. Independent of
abundance, phytoplankton diversity has been correlated inversely with concentrations of nutrients, particularly phosphate. The data collected thus far suggest that variation in plankton communities within Mission Bay may be
influenced by spatial variation in nutrient availability and hydrographic conditions, both of which are related to water circulation.

A Fourteen-Year Assessment Of Fishes In Mission Bay Surveyed With Experimental Gillnets.

Authors: M.A. Shane, Presenter, Hubbs-Sea World Research Institute, 2595 Ingraham Street, San Diego, CA, 92109, 619-226-3946 (W), 619-226-3944 (F), mshane@hswri.org; M.A. Drawbridge, Hubbs-Sea World Research Institute, 2595 Ingraham Street, San Diego, CA, 92109, 619-226-3870 (W), 619-226-3944 (F), mdrawbr@hswri.org.

Abstract: Since 1988 the fish populations in Mission Bay San Diego, California have been sampled with multiple-mesh gillnets. During this 14-year sampling period data was analyzed from 550 hours of effort (324 overnight sets) in Mission Bay. Trends in CPUE were examined for 4 fish categories (sport fishery, elasmobranches, embiotocids, and sciaenids). The CPUE for most species remained somewhat constant during this time period. However, CPUE for leopard shark, gray smoothound, and yellowfin croaker have consistently increased throughout the 14-year period.

Wetland Research In Mission Bay.

Authors: Drew M. Talley, Department of Evolution and Ecology, University of California Davis, Lisa A. Levin, Scripps Institution of Oceanography, University of California San Diego

Abstract: The wetlands located in the back of Mission Bay include salt marsh, tidal flat and sea-grass beds. Much of this is a remnant of a once-extensive wetland – but there are also 7 acres of recently restored salt marsh habitat. These areas form a reserve jointly owned by UC San Diego and the City of San Diego and this has been the site of much research during the past 3 decades. Investigations have focused on marsh plants, algae, invertebrates, fishes and how they interact with sediments and each other. Research themes have included effects of invasive species, recovery of restored marsh ecosystems, trophic interactions, diversity, habitat linkages, and larval dispersal. This presentation will highlight the important role played by Mission Bay in developing understanding of wetland ecology along the Pacific coast.

CAERS website: http://online.sfsu.edu/~caers/welcome.htm