Ecosystem functioning approach applied to a large contaminated coastal site: the study case of the Mar Piccolo of Taranto (Ionian Sea)

Abstract

Knowledge on ecosystem functioning can largely contribute to promote ecosystem-based management and its application. The Mar Piccolo of Taranto is a densely populated area at a high risk of environmental crisis. Here, planktonic primary production (PP) and heterotrophic prokaryotic production (HPP) were measured as proxies of functioning in three sampling sites located in two inlets at different levels of industrial contamination, during three sampling surveys (June 2013, February and April 2014). To have a better overall view and provide some insights into the benthic-pelagic coupling, we integrated PP and HPP in the water column with those in the sediments and then discussed this with the origin of the organic matter pools based on analysis of stable isotopes. Heavy metals and polychlorobiphenyls (PCBs) were also analysed in the surface (1 cm) sediment layer and related to the overall ecosystem functioning. Multidimensional scaling (MDS) analysis, based on the main data, clearly separated the second inlet from the first one, more severely impacted by anthropogenic activities. The stable isotope mixing model suggested the prevalent terrestrial/riverine origin of the particulate organic matter pools (mean 45.5 %) in all sampling periods, whereas phytoplankton contributed up to 29 % in February. Planktonic PP and HPP rates followed the same pattern over the entire study period and seemed to respond to phytoplankton dynamics confirming this community as the main driver for the C cycling in the water column. On the contrary, benthic PP rates were almost negligible while HPP rates were lower or comparable to those in the water column indicating that although the Mar Piccolo is very shallow, the water column is much more productive than the surface sediments. The sediment resuspension is likely responsible for a pulsed input of contaminants into the water column. However, their interference with the proper functioning of the pelagic ecosystem seems to be limited to the bottom layers.

Estuarine circulation in the Taranto Seas

“…Knowledge of these features is not only interesting from a hydrodynamic processes point of view, but it is crucial for understanding the nutrient distribution with its consequences on the trophic net ) and on ecosystem productivity (Cibic et al 2015), as well as to assess the role of the basin in terms of nursery and connectivity (Gulorget and Perthuisot 1992;Belmonte et al 2013;Ghezzo et al 2014). Moreover, because of the Taranto Seas relevance in terms of polluted sediment management, also the circulation effect on the bottom stress was investigated since crucial for studies on sediment transport and on pollutant fate and dispersion processes (Cardellicchio et al 2006;Cardellicchio et al 2015;Di Leo et al 2015;Cassin et al 2015).…”

Continuous and High Transport of Particles and Solutes by Benthos in Coastal Eutrophic Sediments of the Pomeranian Bay

“…We suggest that in this situation the model approach is not suitable for an extraction of reworking rates. In temperate regions, like the Pomeranian Bay, primary production follows a relatively regular seasonal pattern with a maximum in spring and a smaller secondary fall maximum (e.g., Graf, 1992;Sun et al, 1994). The chloropigment inventories at the study sites in general follow this pattern with slightly higher spring values (Figure 4).…”

“…Transport processes in the solute phase (bioirrigation) primarily determine the oxidation status of the sediment by a downward transport of dissolved oxygen from the water column into the sediment and a release of reduced/adsorbed compounds like ammonia, phosphate, hydrogen sulfide, or methane (e.g., Aller, 1982). Particle reworking by fauna (particulate phase transport) often causes a rapid downward transport of labile fresh organic material derived from the water column (e.g., Graf, 1992), a slower transport of inorganic particles in the same direction, and may be responsible for the release of particle-associated contaminants due to changing redox conditions (e.g., Emerson et al, 1984;Kersten, 1988). Bioturbation is considered sensitive to anthropogenic drivers (Griffiths et al, 2017), but its effects on ecosystem functioning remain unclear.…”

A multidisciplinary approach to study confined marine basins: the holobenthic and merobenthic assemblages in the Mar Piccolo of Taranto (Ionian Sea, Mediterranean)

“…The bottom values were quite constant, except for station 1F again and stations 2E and 2F close to the mouth of some drainage channels. The sea water, both at the surface and over the bottom, was well oxygenated, presumably due to the high phytoplankton production, as investigated by Cibic et al (2015). The pH values were quite homogeneous throughout the study area, ranging between 8.2 (1E surface, 2H and 2L bottom) and 8.6 (1A and 2I bottom) ( Table 1).…”