Annalisa Franzo

Benthic ecosystem functioning in the severely contaminated Mar Piccolo of Taranto (Ionian Sea, Italy): focus on heterotrophic pathways

The benthic ecosystem functioning is a rarely applied holistic approach that integrates the main chemical and biological features of the benthic domain with the key processes responsible for the flux of energy and C through the system. For the first time, such conceptual model, with an emphasis on the heterotrophic pathways, has been applied to the sediments at four stations within one of the most polluted coastal areas in Italy: the Mar Piccolo of Taranto. The functioning of the benthic ecosystem was different according to the investigated site. Nearby the military arsenal, i.e., the main source of organic contaminants and heavy metals, the system seemed inhibited at all the investigated structural and functional levels. Slow microbial processes of C reworking together with very limited densities of benthic fauna suggested a modest transfer of C both into a solid microbial loop and to the higher trophic levels. On the other hand, the ingression of marine water through the “Navigabile” channel seemed to stimulate the organic matter degradation and, consequently, the proliferation of meiofauna and macrofauna. In the innermost part of the basin, the system functioning, to some extent, is less impacted by contaminants and more influenced by mussel farms. The organic matter produced by these bivalves fueled faster C reworking by benthic prokaryotes and enhanced the proliferation of filter feeders.

Microphytobenthic response to mussel farm biodeposition in coastal sediments of the northern Adriatic Sea.

The effects of long-line mussel farming on microphytobenthos were investigated in a coastal area of the Gulf of Trieste. Sediment grain-size, organic matter content, microalgal abundance and community structure were analysed in September 2008 and March 2009. Four areas were sampled: a twenty-year farm, a four-year farm, a disused farm and a reference site. Principal component analysis (PCA) highlighted a decreasing gradient of organic matter content from the twenty-year farm to the control. Mussel farming seemed to influence microphytobenthic abundance with higher densities in the oldest farm. Three genera were dominant; Navicula and Gyrosigma seemed to be stimulated by the organic load under the active farms while we infer that Nitzschia proliferation was limited by shade caused by mussel ropes. In the PCA, samplings of the disused farm were placed in-between the still active farms and the control, indicating the partial recovery occurred in this site.

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

This study is a rare example of “the ecosystem approach to management” that has been carried out for the purpose of providing practical support to decision-makers in managing a Site of National Interest (SIN) where activities such as fishing, aquaculture and swimming are restricted. Benthic ecosystem functioning was assessed to verify whether it would be possible to exclude the less contaminated part from the SIN and its legislative constraints. At five macrosites subjected to diversified industrialization and anthropization, we evaluated the structural characteristics of the sediments, both heterotrophic and phototrophic communities, and the main processes of production, transformation and consumption of organic matter at seven stations, plus a reference site. Along the north-eastern boundary of the bay, the port, shipbuilding and iron foundry areas, characterised by high levels of contaminants, low macrozoobenthic diversity, major organic contents (up to 51.1 mgC g-1) and higher numbers of hydrocarbon degrading bacteria (up to 5,464 MPN gdry-1), differed significantly (RANOSIM = 0.463, p = 2.9%) from the other areas (stations). Oxygen consumption (-15.221.59 mgC m-2) prevailed over primary production and the trophic state was net heterotrophic. In contrast, on the other side of the harbour (residential area/centre bay), contamination levels were below the legal limits and both the microalgal and macrobenthic communities displayed higher biodiversity. Higher macrofaunal abundances (up to 753174.7 ind.m-2), primary production rates (up to 58.608.41 mgC m-2) and exoenzymatic activities were estimated. nMDS and SIMPROF analyses performed on benthic communities significantly separated the most contaminated stations from the other ones. Overall, by applying this holistic approach, a better environmental situation was highlighted along the southern boundary of the bay and according to these results this part of the bay could be excluded from the SIN. However, further sampling is required along a finer sampling grid in the less contaminated side of the port in order to confirm these first results. Our work is one of the first case studies where such an ecosystem approach has been applied to a port area, in order to provide practical support to decision-makers involved in the spatial planning of harbour zones.

Foam production as a side effect of an offshore liquefied natural gas terminal: how do plankton deal with it?

The future growing demand of fossil fuels likely will lead to an increased deployment of liquefied natural gas terminals. However, some concerns exist about their possible effects on the marine environment and biota. Such plants showed to cause the production of foam, as occurred at the still operative terminal of Porto Viro (northern Adriatic Sea). Here, we present results from two microcosm experiments focused on the effects of such foam on microbially mediated degradation processes and its consequent incorporation within the pelagic food web. Such material could be considered as a heterogeneous matrix of both living and non-living organic matter, which constitutes an important substrate for exoenzymes as suggested by the faster hydrolytic rates measured in the treatment microcosms. In the second experiment, a quite immediate and efficient carbon transfer to planktonic biomass through prokaryotic incorporation and consequent predation by heterotrophic flagellates was highlighted. Although no negative effect was evidenced on the overall microbes’ growth and foam-derived C seemed to be easily reworked and transferred to higher trophic levels, an important reduction in biodiversity was evidenced for microalgae. Among them, mixotrophic organisms seemed to be favoured suggesting that the addition of foam could cause a modification of the microbial community structure.

Meiofaunal communities in four Adriatic ports: Baseline data for risk assessment in ballast water management

Ports receive a variety of contaminants related to a wide range of anthropogenic activities - including ship ballast water (BW) - that ultimately find their way to sediments. Benthic meiofauna from four Adriatic ports (Ancona, Trieste, Koper, and Split) was assessed for the main environmental pollutants, to evaluate the effects of human activities on meiobenthos and identify the most appropriate descriptor to assess the ecological quality of marine ecosystems. Sediment analysis demonstrated that Trieste and Split were the most contaminated ports, followed by Koper and Ancona. All meiofaunal parameters showed high spatial and temporal variability, in line with the marked heterogeneity of the four ports. Sand, total organic carbon, and pollutants seemed to be the variables that best explained meiofaunal patterns. Community structure and rare taxa were the meiofaunal descriptors that reflected the environmental status and biological response most accurately. The present data suggest that meiofauna can be used to assess the biological impact of BW.

Effects of CO2 Induced pH Decrease on Shallow Benthic Microbial Communities

Two mesocosm experiments (18 and 10°C) have been carried out in order to investigate the effects of pH reduction due to pCO2 increase on benthic microbial communities collected from the Gulf of Trieste (Northern Adriatic Sea). During each experiment 3 mesocosms with different pH values were set up (6.5, 7 and an aerated control ~ 8). The analyses focussed on prokaryotic abundance, degradation processes and prokaryotic carbon production. Preliminary results highlight differences in metabolic response to CO2 in terms of organic matter degradation patterns whereas prokaryotic numbers and C production seemed to be less affected by pH decrease.