Patterns and Predictors of Phytoplankton Assemblage Structure in a Coastal Lagoon: Species-Specific Analysis Needed to Disentangle Anthropogenic Pressures from Ocean Processes

Abstract

Phytoplankton are dominant primary producers and key indicators in aquatic ecosystems. Understanding the controlling factors on the structure of phytoplankton assemblages is fundamental, but particularly challenging at the land–ocean interface. To identify the patterns and predictors of phytoplankton assemblage structure in the Ria Formosa coastal lagoon (south Portugal), this study combined phytoplankton abundance along a transect between the discharge point of a wastewater treatment plant and a lagoon inlet, over two years, with physico-chemical, hydrographic, and meteo-oceanographic variables. Our study identified 147 operational taxonomic units (OTUs), and planktonic diatoms (60–74%) and cryptophyceans (17–25%) dominated the phytoplankton in terms of abundance. Despite strong lagoon hydrodynamics, and the lack of spatial differences in the phytoplankton abundance and most diversity metrics, the multivariate analysis revealed differences in the assemblage structure between stations (p < 0.001) and seasons (p < 0.01). Indicator analysis identified cryptophyceans as lagoon generalists, and 11 station-specific specialist OTUs, including Kryptoperidinium foliaceum and Oscillatoriales (innermost stations) and potentially toxigenic species (Pseudo-nitzschia and Dinophysis; outer lagoon station, p < 0.05). Water temperature, pH, and nutrients emerged as the variables that best explained the changes in the phytoplankton assemblage structure (p < 0.001). Our findings provide insight into the relevance of local anthropogenic and natural forcings on the phytoplankton assemblage structure and can be used to support the management of RF and other coastal lagoons.

Analysis of the Impact of Hydraulic Gates on a Stabilized Tidal Inlet Structure: Mathematical Model and Data Measurements

“…The modeling of STIS has been studied as an integral part of estuarine systems, considering the mathematical behavior of hydraulic devices [1,17], which is of utmost importance since its operation also plays an essential role in treating issues related to water quality in estuarine systems [18][19][20].…”

Nitrogen and phosphorus uptake kinetics in cultures of two novel picoplankton groups responsible for a recent bloom event in a subtropical estuary (Indian River Lagoon, Florida)

“…However, disentangling the complex interactions between the conventional "bottom-up" (e.g., nutrients) and "topdown" (e.g., grazing) controls on bloom formation, as well as other biogeochemical factors, such as climatic and hydrologic conditions, have complicated efforts to model HAB dynamics (Burkholder et al, 2006;Glibert et al, 2010;Gowen et al, 2012;Davidson et al, 2014;Rothenberger and Calomeni, 2016;Glibert et al, 2023). It is also recognized that modeling and managing HABs requires information on the character (e.g., toxin, motility, size, growth rates) of the dominant species involved in the blooms and the specific factors that select for its success (e.g., nutrient preferences, temperature and light optima) (Burford et al, 2020;Glibert, 2020;Glibert et al, 2023;Lima et al, 2023). In this study we examined the nutrient preferences of the phytoplankton species that dominated a major bloom event in the Indian River Lagoon and discuss how these preferences may have contributed to in their success.…”