All-In-One: Microbial Response to Natural and Anthropogenic Forcings in a Coastal Mediterranean Ecosystem, the Syracuse Bay (Ionian Sea, Italy)

Abstract

Bacterial and phytoplankton communities are known to be in close relationships, but how natural and anthropogenic stressors can affect their dynamics is not fully understood. To study the response of microbial communities to environmental and human-induced perturbations, phytoplankton and bacterial communities were seasonally monitored in a Mediterranean coastal ecosystem, Syracuse Bay, where multiple conflicts co-exist. Quali-quantitative, seasonal surveys of the phytoplankton communities (diatoms, dinoflagellates and other taxa), the potential microbial enzymatic activity rates (leucine aminopeptidase, beta-glucosidase and alkaline phosphatase) and heterotrophic culturable bacterial abundance, together with the thermohaline structure and trophic status in terms of nutrient concentrations, phytoplankton biomass (as Chlorophyll-a), and total suspended and particulate organic matter, were carried out. The aim was to integrate microbial community dynamics in the context of the environmental characterization and disentangle microbial patterns related to natural changes from those driven by the anthropic impact on this ecosystem. In spite of the complex relationships between the habitat characteristics, microbial community abundance and metabolic potential, in Syracuse Bay, the availability of organic substrates differently originated by the local conditions appeared to drive the distribution and activity of microbial assemblage. A seasonal pattern of microbial abundances was observed, with the highest concentrations of phytoplankton in spring and low values in winter, whereas heterotrophic bacteria were more abundant during the autumn period. The autumn peaks of the rates of enzymatic activities suggested that not only phytoplankton-derived but also allochthonous organic polymers strongly stimulated microbial metabolism. Increased microbial response in terms of abundance and metabolic activities was detected especially at the sites directly affected by organic matter inputs related to agriculture or aquaculture activities. Nitrogen salts such as nitrate, rather than orthophosphate, were primary drivers of phytoplankton growth. This study also provides insights on the different seasonal scenarios of water quality in Syracuse Bay, which could be helpful for management plans of this Mediterranean coastal environment.

Phytoplankton and Bacterial Communities’ Patterns in a Highly Dynamic Ecosystem (Central Mediterranean Sea)

“…Conversely, in the IIW an abrupt decrease in all the assayed enzymes suggests that the microbial metabolism was limited. Although our values were similar to those measured for LAP [92], they exceeded by 1-2 magnitude orders those previously reported in other Ionian areas for AP [19,92,93] and by 3 or 4 times those of GLU [94].…”

“…Previous studies described microbial communities as potential descriptors of environmental quality [13][14][15][16]. As heterotrophic bacteria utilise the available organic carbon substrates [9], both microbial abundance and functions undergo significant changes in response to environmental variability [17][18][19]. Variations in environmental and biological forcings have been related to those in cell morphological traits [20].…”

A Snapshot of the Taxonomic Composition and Metabolic Activity of the Microbial Community in an Arctic Harbour (Ny-Ålesund, Kongsfjorden, Svalbard)

“…Harbours are areas of economical relevance exposed to strong impacts from shipping, as well as urban and industrial waste, and consequently environmentally sensitive to anthropogenically derived pressure [1][2][3]. Intense maritime traffic, together with the low hydrodynamism of these sheltered bays, results in the organic matter enrichment of the waters, giving rise to anoxia and eutrophication events [4][5][6][7]. Traditionally, environmental characterisation of harbours regarded their chemical contamination-related features [1,4,5].…”

Phytoplankton Community Response to Environmental Factors along a Salinity Gradient in a Seagoing River, Tianjin, China

“…Besides this, nutrients have always been the focus of phytoplankton research, and they should be ascribed much responsibility for algal blooms [ 3 , 7 , 25 ]. Studies have proved that phytoplankton community, species richness, community diversity, and species abundance (e.g., cyanobacteria bloom) are all closely related to nutrient concentrations [ 4 , 23 , 26 , 27 ]. In recent years, the impact of salinity on phytoplankton has received much attention.…”