44-6 Variation in Bryozoan Feeding Ecology Along a Coastal Productivity Gradient

Session: Paleontology, Paleoecology/Taphonomy, Phylogenic Morphological Patterns (Posters)

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Abstract:

Human-induced nutrient enrichment has significantly augmented coastal primary productivity globally. Resulting changes in primary productivity and dissolved oxygen concentrations can have profound impacts on benthic organisms. Cupuladriid bryozoans — suspension-feeding colonial invertebrates that inhabit tropical continental shelf environments — may alter their ecomorphological traits in response to these environmental changes. The size of the orifice, the opening through which the lophophore (feeding structure) extends, controls the size of phytoplankton that can be ingested and possibly also the colony’s feeding rate. Larger orifice areas correlate with larger lophophores, which could enable higher suspension-feeding rates. We hypothesized that orifice size varies with regional primary productivity across the northern Gulf of Mexico. Specifically, we expected larger orifices in less productive environments and smaller orifices in more productive environments, as increased feeding capacity could benefit organisms living in environments where food is limited. Dead-collected bryozoan colonies were separated from benthic samples collected along the -20m isobath in two regions, Florida (FL), and Alabama (AL). Bryozoan colonies were identified to species, categorized by their reproductive mode (clonal vs. aclonal), and analyzed using light and scanning electron microscopy. Measurements of orifices and autozooids were extracted from SEM images using the DeepBryo software. Statistical analyses were conducted in RStudio to evaluate regional differences within species. Regional variations in orifice area were observed in both Discoporella depressa and Reusirella doma, with D. depressa having larger orifice areas in the more productive waters offshore of AL and R. doma having larger orifice areas in the less productive waters offshore of FL. Additionally, larger autozooid areas were observed in R. doma offshore of FL; however, D. depressa showed no clear regional difference in autozooid area. Variations in orifice size for these two species are correlated with regional differences in net primary productivity, however these two species exhibit contrasting trends. This indicates species-specific changes in feeding ecology in response to regional environmental conditions, with R. doma exhibiting patterns consistent with our expectation above and D. depressa deviating from that expectation. These opposing patterns suggest that factors other than net primary productivity, such as variation in phytoplankton size between eutrophic versus oligotrophic settings, may play an important role. Future work will focus on disentangling the environmental drivers responsible for these species-specific responses.

Geological Society of America Abstracts with Programs. Vol. 58, No. 2, 2026

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