Benthic diatoms are a major component of biofilms that form on surfaces submerged in marine environments. Roughness of the underlying substratum affects the settlement of both diatoms and subsequent macrofouling colonizers. This study reports the effects of roughness on estuarine diatom communities established in situ in the Indian River Lagoon, FL, USA. Natural communities were established on acrylic panels with a range of surface roughnesses. Smoother substrata exhibited higher cell density, species richness, and diversity. Twenty-three of 58 species were found either exclusively or more abundantly on the smooth surfaces compared to one or both roughened treatments. The results suggest a greater ability of benthic diatoms to recruit and colonize smooth surfaces, which is probably explained by a higher degree of contact between the cells and the surface.

To examine the role of substratum concavity in determining oyster [Crassostrea virginica (Gmelin, 1791)] settlement success, laboratory settlement was examined on natural and artificial substrata of various concavities, defined by width-to-depth (W:D) ratio. Experiments were conducted in 204-l capacity laboratory flumes. Concavities tested include W:D ratios of 2, 5, and 16, plus a flat surface for control comparisons. Active settlement, passive settlement, and flow around these concavity treatments were examined. In addition, settlement on oyster shell cultch presented in different surface orientations, and either zip-tied to open mats, or packed in mesh bags, was examined. Results indicate that concavity can affect settlement success (W:D ratio of 5 resulted in the highest settlement success under this study's conditions). Examination of flow rates and patterns suggests that water movement over W:D 5 treatments delivers larvae to the settlement surface, but active attachment behavior is require...

To quantify the ecological impacts of organic sediments and environmental dredging, benthic mollusks were chosen as bioindicators of environmental change, measured as sediment organic content and associated parameters. Data on species richness, ecological diversity (which was measured as biodiversity), and abundances were collected alongside sediment and near-bottom water quality data before, during, and after environmental dredging. Organic sediment content was found to have an inverse logarithmic relationship with benthic mollusk biodiversity, species richness, and abundance. Post hoc analyses found that percent dissolved oxygen, which correlates with sediment organic content, was responsible for 29.31–34.12% of the benthic mollusk community variation. Sediments with lower organic content had higher biodiversity (organism densities up to 1 organism m⁻²), abundance (over 2.0 × 10⁵ organisms m⁻²), and species richness (organism densities up to 4 organisms m⁻²). In comparison, sediments with higher organic content had low biodiversity (organism densities 0–1 organisms m⁻²), abundance (as low as 0 organisms m⁻²), and species richness (organism densities as low as 0 organisms m⁻²).