Microbenthic community structure and trophic status of sediments in the Mar Piccolo of Taranto (Mediterranean, Ionian Sea)

Abstract

This study aimed to assess the benthic ecosystem trophic status in a heavily polluted marine area and the response of the microbenthic community to multiple and diffuse anthropogenic impacts, integrating information coming from the active and resting (plankton's cysts) components of microbenthos. Two sampling campaigns were carried out in the period 2013-2014 and four sampling sites at different levels of industrial contamination were chosen within the first and second inlet of the Mar Piccolo of Taranto. The chemical contamination affected to a higher extent the active microbenthos than the resting one. In the central part of the first inlet, characterised by more marine features, thrives a very rich and biodiverse microbenthic community. In contrast, at the polluted site near the military navy arsenal, extremely low densities (9576 ± 1732 cells cm(-3)) were observed for active microbenthos, but not for the resting community. Here, the high level of contamination selected for tychopelagic diatom species, i.e., thriving just above the surface sediments, while the other life forms died or moved away. Following the adoption of a 10 μm mesh, for the first time, resting spores produced by small diatoms of the genus Chaetoceros were found. Our results further indicate that although the Mar Piccolo is very shallow, the benthic system is scarcely productive, likely as a consequence of the accumulated contaminants in the surface sediments that probably interfere with the proper functioning of the benthic ecosystem.

The Port of Trieste (Northern Adriatic Sea)—A Case Study of the “Ecosystem Approach to Management”

“…This further indicates that benthic microalgae were able to adapt to stress induced by high levels of chemical compounds accumulated in these sediments. In contrast, Rubino et al (2016) estimated extremely low primary production rates (close to zero) in a shallow area of the Ionian Sea severely contaminated by PCBs and heavy metals. The authors infer that the synergistic effect of the contaminants was such as to interfere with the proper functioning of certain benthic processes, i.e., microalgal photosynthetic capability.…”

“…sediments of the Mar Piccolo of Taranto (Ionian Sea, Italy), where only few diatom specimens were encountered at the most contaminated site (Rubino et al, 2016). The authors reported that only those diatoms that thrive just above the surface sediments, i.e., Paralia sulcata and Bacillaria paxillifera, rather than within the sediments, survived the extremely high concentrations of PCBs and heavy metals, whereas diatoms with other life strategies likely died.…”

“…However, the minimum (as absolute number) observed in the iron foundry area was still two times lower than that previously reported for a riverine-lagoonal system that was strongly heterotrophic (−12.00 mg C m −2 h −1 ) (Cibic et al, 2012b), where the major oxygen demand was due to degradation of the high organic load. We further compared our values to those reported from the severely contaminated Mar Piccolo of Taranto, where the trophic state of the benthic system was net heterotrophic at all sites and during both seasons (April and June), with values ranging from −3.62 mg Cm −2 h −1 to −8.17 mg C m −2 h −1 (Rubino et al, 2016).…”

“…Many studies report on changes in abundance or diversity of microor macrobenthic communities in chronically polluted marine environments. Other fundamental aspects, such as how pollution affect respiration rates, primary production (Sundbäck et al, 2004;Forster et al, 2006;Rubino et al, 2016), prokaryotic heterotrophic production or other microbial processes (Manini et al, 2004;Pusceddu et al, 2014;Sweetman et al, 2014;Franzo et al, 2016a) have seldom been analyzed in chemically polluted environments. Studies on benthic ecosystem functioning, based on actual estimates of biological processes integrated with the qualitative and quantitative composition of communities at different trophic levels, are even rarer (Schaffner et al, 2008;Cibic et al, 2012b;Franzo et al, 2016b).…”

Integrated environmental characterization of the contaminated marine coastal area of Taranto, Ionian Sea (southern Italy)

“…Moreover, photoautotrophic and heterotrophic benthic functional pathways are addressed separately in two papers. Rubino et al (2015) assess the benthic ecosystem trophic status and the response of the active and resting components of the microbenthic community to multiple and diffuse anthropogenic impacts. Finally, the heterotrophic pathways of the benthic ecosystem functioning are addressed by Franzo et al (2015), by considering both its structural (prokaryotes, meiofauna, and macrofauna) and functional (microbial processes of C reworking) levels.…”