Phytoplankton composition in the subtropical coastal shelf environment of Cape Canaveral, Florida

Abstract

The abundance and composition of the phytoplankton community off the coast of Cape Canaveral, Florida was examined from Fall 2013 to Summer 2015. The region is a shallow shelf environment. Water samples were collected quarterly at 24 sites from the surface and bottom of the water column; temperature and nutrient concentrations were determined. Photoautotrophic picoplanktonic prokaryotes were consistently important in terms of numerical abundance and biomass throughout the study. Among the cyanobacteria, a surface bloom of the nitrogen-fixing filamentous species Trichodesmium was observed in Fall 2013. Dinoflagellates and diatoms were also major contributors to phytoplankton biomass. Many of the dominant dinoflagellates were mixotrophic or heterotrophic species. Nanoplanktonic eukaryotic algae were also periodically an important group in terms of biomass, such as prasinophytes (Chlorophyta). No consistent and reoccurring spatial patterns were observed, likely due to the dynamic water circulation in the open Cape Canaveral shelf environment. Depth-related differences in biomass were observed for dinoflagellates and diatoms. Dinoflagellate biomass was on average higher in surface samples, related to their motility. Conversely, diatom biomass was on average higher in bottom waters, reflecting the negative buoyancy of most species and the potential for re-suspension of cells from the sediment surface. The strong increase in the importance of photoautotrophic picoplanktonic prokaryotes biomass observed in Year 2 of the study may reflect the influence of high rainfall resulting from El Niño conditions on nutrient loads from regional land masses, as indicated by increases in phosphorus concentrations.

Seasonality of phytoplankton biomass and composition on the Cape Canaveral shelf of Florida: Role of shifts in climate and coastal watershed influences

“…The study showed that ciliates on average represent over a third of total zooplankton biomass. The same study also showed that picoand nano-phytoplankton taxa represented on average over 50% of total phytoplankton biomass (Tate et al, 2020). Since ciliates are known to be a 10.…”

“…Mean TN levels often remained between 0.1-0.25 mg L −1 . Notably, the high levels of TN in the fall of 2013 coincided with a bloom of the nitrogen-fixing cyanobacterium Trichodesmium erythraeum (Tate et al, 2020). Mean total phosphorus concentrations ranged from 0.007 ± 0.001 mg L −1 to 0.033 ± 0.004 mg L −1 in summer 2018 and in spring 2015, respectively, (Figure 7).…”