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We examined bacterioplankton abundance and metabolic characteristics in northern San Francisco Bay, California during spring and summer 1996 at three sites: Central Bay, Suisun Bay and the Sacramento River. These sites spanned a salinity gradient from marine to freshwater, and sampling occurred during a period of seasonally declining river flow. The microbial measures included radio-labeled amino acid uptake (L-leucine, L-proline, L-serine), ectoenzyme activity (aminopeptidase and 13-D-glucosidase), and bacterial abundance using lum filters to separate free from particle-associated bacteria. We observed a seasonal decline in all bacterial metabolic measures at all stations, suggesting that a system-wide variable may be important in controlling bacterial activity. One such variable is freshwater flow into the Bay (as a proxy for organic matter flux), which positively covaried with all metabolic measures. We also observed a sharp decline in particle-associated bacteria in Suisun Bay and the Sacramento River between July and August. This may be due to combined effects of declining nutritive value of the aging particles, and increasing grazing pressure by benthic filter feeders. Aminopeptidase activity was positively related to increasing salinity and 13-D-glucosidase was negatively related to increasing salinity, indicating a gradient in the relative quality of organic matter from carbohydrate-rich riverine to protein-rich oceanic materiaL Overall, Suisun Bay had the highest proportion of particle-associated bacteria (avg. 49%), followed by Sacramento River (avg, 36%) and Central Bay (avg. 11%), Particles were the sites of enhanced ectoenzyme activity, but not amino acid incorporation. Therefore bacteria may be actively dissolving the particulate organic matter but their growth rates are not significantly enhanced on particles.

Heterotrophic dinoflagellates and ciliates in the Sargasso Sea near Bermuda show temporal variability in their distribution, abundance, biomass and size composition during spring and summer conditions. The dinoflagellates and ciliates have similar biomass, and the former have > 5 micro meters microprotist assemblage. The microprotists are more abundant during summer, but the dinoflagellates are always more abundant than the ciliates. Majority of the dinoflagellate cells are < 20 micro meters in size, while the ciliates show more heterogeneous size distributions.

Benthic invertebrate community composition was surveyed across the salinity gradient of the Pensacola Bay Estuary in Florida during summer 2016. Macrofauna densities ranged from 1000 to 9300 individuals m−2, with highest densities occurring at the upper estuary and the lowest in the mid‐ and lower estuary. Taxonomic richness and Shannon diversity were lowest in the upper estuary and increased along the salinity gradient. Small‐bodied, near‐surface infaunal polychaete species (e.g., Mediomastus ambiseta and Paraprionospio alata) dominated the macrofaunal community in fine sediment areas. We calculated the Gulf of Mexico Benthic Index of Biological Integrity for each site and compared the index scores with those from Environmental Monitoring and Assessment Program ‐ Estuaries, an earlier benthic assessment model. Condition evaluations by the different models did not match across all sites in this study; however, scores consistently indicated that most sites were at or near degraded levels, implying that Pensacola Bay represents a marginal habitat for a "healthy" benthic macrofauna community. This study provided new information about the benthic communities and sediments in the Pensacola Bay estuary. Integr Environ Assess Manag 2020;16:245–256. Published 2019. This article is a US Government work and is in the public domain in the USA. KEY POINTS: Study describes benthic communities in the Pensacola Bay system, in the Gulf of Mexico (GOM), and evaluates habitat condition using 2 benthic index approaches, i.e., GOM Benthic Index of Biological Integrity (B‐IBI) and Environmental Monitoring and Assessment Program ‐ Estuaries (EMAP‐E).Results of this study suggest that more systematic testing and reference site assessments are needed to make the GOM B‐IBI more useful for environmental management applications, particularly for high‐salinity regions of northern Florida estuaries with muddy sediments.Until the GOM B‐IBI can be refined to include panhandle‐specific metrics, the EMAP‐E index may be the most appropriate model for assessing the benthic habitat condition in this region. [ABSTRACT FROM AUTHOR]

The article presents a study on phytoplankton nutrient limitation in a sub-estuary of lower Pensacola Bay in Florida. Nutrient-addition bioassays showed year-round nutrient limitation, opposing seasonal patterns often describes for higher-latitude estuaries. Combined Nitrogen (N) and Phosphorus (P) additions heightened the growth of phytoplankton more than single nutrients. In-situ alkaline phosphatase (Pase) acitivity was unclearly related to inorganic nutrient concentrations or ratios. Changes in Pase activity after nutrient additions were consistent with the other bioassay data, however. The results indicated that Pensacola Bay would be sensitive to advanced N and P loadings, increasing phytoplankton production and yield with potentially negative ecosystem outcomes.