Nutrients and Plankton

Water quality measurements were taken by each of the three different sampling protocols for hydrology, limnological and fisheries, and invertebrate. Hydrology sampling included measuring the salinity gradient within the ponds at four or five fixed places in the corners of the ponds. Fisheries and limnology sampling, and invertebrate sampling included examining spatial correlation of within-pond variation in water quality by taking measurements in each of the ten random grids that were sampled bimonthly. Analysis was conducted on nutrient concentrations, algal community primary productivity, and zooplankton community taxonomic composition.

Preliminary analysis on the zooplankton samples for the May-Jun 1999 samples are currently being conducted. These analyses also show a change of species composition between ponds. Acartia tonsa are the dominant copepod in lower salinity ponds and Artemia salina are dominant in the high salinity ponds.

Pelagic and Benthic Invertebrates

A general invertebrate species list was developed for all of the ponds and variations among ponds were identified. In the benthic samples, over 40 different taxa groups were identified, most to the family and genus taxonomic levels. The most diverse group was the polychaete worms, with 13 different genera present, mostly in Ponds 1 and 2. We also identified six species of bivalves, 10 crustacea taxa, four insect families, and seven miscellaneous taxa. The greatest number of taxa occurred in Ponds 1 and 2. Pond 3 had notably fewer taxa (10), followed by Pond 4 (3 taxa) and Pond 7 (2 taxa). We found correlation between increasing salinity and decreasing taxa richness, and polychaetes and bivalves decreased rapidly.
See topo map showing the salt pond locations or infrared photo of marsh for reference.

In the sweep samples, we identified 19 taxa although nine are more appropriately part of the benthos, rather than zooplankton organisms. Of the zooplankton taxa, Mysis and Cumacea were predominant in Pond 1. Very few organisms were collected in sweeps in Pond 2, although Daphnia, Copepoda and Cumacea were found. In Pond 3, Corixinae were present in sweep samples in relatively low numbers. Artemia were very abundant in Pond 4 and were present but not abundant in Pond 7.
See topo map showing the salt pond locations or infrared photo of marsh for reference.

Aquatic Macrophytes

We examined the distribution of plants along line transects and in quadrats in Pond 2a during Mar-Apr and Sept-Oct 1999. Species composing < 1% of the samples were recorded as "present" in the transect or quadrat. Dominant species include Salicornia virginica, Scirpus maritimus, Spartina foliosa, and Typha latifolia.

Estuarine Fishes

We capture fish in Ponds 1, 2, 2a, and 3, but none in Ponds 4 and 7. Species richness of fish in ponds declined inversely to salinity. In Pond 1, we captured 10 species compared with 6 species in Pond 2 and 5 species in Pond 3. Within the ponds, there is a comparatively numerous population of prey fish in Pond 1 and a comparatively low prey fish population in Pond 2 (see graph of fish counts). The slope of the length-weight equation for striped bass was much greater in Pond 1 than in Pond 2. The relative weight (Wr) of striped bass greater than 200 mm in Ponds 1 and 2 during Sep-Oct was smaller and not as robust as a curve based on the national average.
See topo map showing the salt pond locations or infrared photo of marsh for reference.

Waterbirds

Numbers and Distribution. -- Fifty-two species and counts of over 100,000 birds were recorded from Jan to Oct 1999 in the ponds (Table 12). Pond 4 contained the greatest number of birds at over 45,000 individuals, whereas ponds 1, 2, 3, 2A, and 7 were substantially lower. Diving benthivores made up the majority of the birds in all the ponds, while dabbling birds are only one-sixth as numerous. Surface feeders, shallow probers and deep probers made up the remainder.
See topo map showing the salt pond locations or infrared photo of marsh for reference.

Diversity and bird community distribution between the ponds seem to be more strongly influenced by water depth than by salinity, with the exception of the pond 7. These differences are evident when the foraging guilds are examined by pond. Ponds 1, 2, 3 and 4 supported the majority of diving benthivores, while Pond 2A, a revegetated pond with shallow open water areas, supported primarily dabbling ducks rather than diving benthivores. The most diverse ponds were Pond 1 (44 species), a muted tidal pond adjacent to San Pablo Bay, and Pond 4 (42 species). These ponds were the most varied water depths as well, with both shallow areas for shorebirds and deeper areas for waterfowl. This diversity in water depths varied spatially in Pond 1, with the southern end typically very shallow and the northern end deeper and temporally in Pond 4, which was relatively deep in the winter and much shallower or dry in the summer.
See topo map showing the salt pond locations or infrared photo of marsh for reference.

Diet Studies. -- We initiated diet collections in the fall of 1999. Birds were not distributed evenly across the ponds, thus sampling was initiated on species found in at least two salinity levels such as American avocets and ruddy ducks found in low and mid salinities. Esophageal contents will be analyzed following the second field season.

Radio Telemetry. -- We obtained 993 radio locations for black-necked stilts (Himantopus mexicanus) banded in the North Bay; 96% of those locations were in North Bay wetlands. Twenty-three of the 26 birds banded in the North Bay stayed in that vicinity for the duration of their individual tracking periods.

Hydrology and Water Quality

Salinity and Hydrodynamics. -- Salinity was primarily influenced by rainfall during the wet season and inter-pond water transfers during the dry season. Pond 4 had very low water levels and very high (>260 ppt) salinity during the late dry season because CDFG could not transfer freshwater into the pond because of ineffective siphons. Variability within ponds was generally small, with the exception of recent freshwater inflow and some wind conditions.