A Re-assessment of Narragansett Bay Benthic Habitat Quality Between 1988 and 2008

The first bay-wide synoptic survey of benthic habitat quality in Narragansett Bay, Rhode Island, USA, was conducted in August of 1988. Twenty years later, we revisited the same sampling locations as the original survey using similar sediment profile imagery technology and analysis tools. Like estuaries throughout the US, increased temperatures and reductions to anthropogenic nutrient inputs have cumulatively affected Narragansett Bay in the intervening 20 years. To understand how these changes may have influenced benthic organic enrichment and habitat quality, we compared the prevalence and spatial arrangement of benthic biotopes (i.e., biotic and abiotic benthic descriptions) between 1988 and 2008 surveys. Biotopes dominated by Ampelisca spp. tubiculous amphipods increased \u3efivefold between 1988 and 2008, and expanded into the more urban, anthropogenically stressed Providence River estuary. Ampelisca beds occurred at critical boundaries in organic enrichment and habitat quality in both years and indicated the quantity of organic matter reaching the benthos. In general, benthic biotopes reflect the degree of benthic-pelagic coupling and are an important link between estuarine water quality and other marine life. As estuaries globally cope with the effects of increased warming and legislated anthropogenic nutrient reductions, rapid assessments of benthic biotopes will be critical for understanding changes to whole-estuary condition as a result of these cumulative stressors

Primary production in a subtropical stratified coastal lagoon contribution of anoxygenic phototrophic bacteria

Anaerobic anoxygenic phototrophic bacteria can be found in the suboxic waters of shallow stratified coastal systems, and may play important roles in the total primary production of subtropical stratified coastal lagoons. We investigated the spatiotemporal variability of light CO2 fixation and net oxygen production in the stratified Conceição Lagoon (Brazil) in summer and fall of 2007, as well as the contribution of bacteriochlorophyll a (BChl a)- containing bacteria to photosynthetically driven electron transfer. Both chlorophyll a (Chl a) and BChl a varied in space, while only BChl a varied in time (three-fold increase from summer to fall). In summer, net oxygen production and light CO2 fixation were correlated, with both having higher rates with higher Chl a concentrations in the enclosed region of the lagoon. In fall, CO2 fixation was decoupled from oxygen production Denaturing gradient gel electrophoresis revealed that bacterial communities of oxic site 12 and suboxic site 33 formed one cluster, different from other oxic samples within the lagoon. In addition, BChl a/Chl a ratios at these sites were high, 40% and 45%, respectively. Light acted as the main factor controlling the BChl a concentration and CO2 fixation rates. High turbidity within the enclosed area of the lagoon explained high BChl a and decoupling between CO2 fixation and oxygen production in oxygenated waters. Contribution of purple sulfur bacteria to total bacterial density in suboxic waters was 1.2%, and their biomass contributed to a much higher percentage (12.2%) due to their large biovolume. Our results indicate a significant contribution of anaerobic anoxygenic bacteria to the primary production of the “dead zone” of Conceição Lagoon