Giant Reed (Arundo donax) wrack as sink for plastic beach litter: First evidence and implication.

In order to maintain the hydraulic outflow in land reclaimed canalizations, the competent agencies provide to mechanically mow the Giant Reed (Arundo donax, L. 1753) along the aquatic ecosystem banks. Nevertheless, the reeds mowed can be transported away from the waters following storm surges and can be deposited in large quantities along the sandy beaches. We carried out a stratified study in a Mediterranean sandy beach to test the hypothesis that Giant Reed wrack may act as a sink and barrier for plastic beach litter. We observed a large amount of plastic litter entrapped in the Arundo donax wrack (density of 0.868 items/m2), with a higher density when compared to both the inner and the shoreline belts. Density of litter is significantly higher considering the categories of meso- and micro-plastics. Organic macrophyte wrack is useful for dunal macrodetritivorous invertebrates and generally for fauna communities, which use this litter as refuge and trophic pabulum. Significant accumulations of organic wrack can mitigate coastal erosion; nevertheless, for its structural characteristics, Arundo wrack can also act as a barrier for litter towards the inner vegetated dunes, so entrapping a large amount of anthropogenic litter. In this regard, Arundo wrack can represent a sink habitat, first attracting (due to large availability of detritus with a relative high rate of decomposition) and then, entrapping many organisms in anthropogenic litter. We suggest that, once mechanically mowed, the land reclaimed agencies should periodically remove from the channel banks the Arundo donax reeds, impeding the accumulation of incoherent vegetated matter along the aquatic ecosystem banks.

Fishing lines and fish hooks as neglected marine litter: first data on chemical composition, densities, and biological entrapment from a Mediterranean beach.

We reported first data on the densities and chemical composition of fishing lines and fish hooks deposited on a Mediterranean beach. On a sampling area of 1.5 ha, we removed a total of 185,028 cm of fishing lines (density 12.34 cm/m2) and 33 hooks (density 22 units/ha). Totally, 637.62 g (42.5 mg/m2) of fishing lines were collected. We sampled 120 items entangled belongings to 7 animal taxa (density 6.49 items/100 m of fishing lines). We also observed a not quantifiable number of egagropiles (Posidonia oceanica spheroids), Rhodophyceae (Halymenia sp.) and segments of reeds of Phragmites communis, trapped in the fishing lines. Fourier transform infrared (FTIR) spectroscopy was used in order to identify the chemical composition of the fishing lines: 92% was made of nylon while 8.0% was determined as fluorocarbon based polymers (polyvinylidene fluoride). Because of their subtlety and reduced size, sandy beach cleaning operations should include at least two consecutive removal samplings: indeed, a part of this litter (12.14%) is not removed in the first sampling. The unexpected high density of fishing lines suggests specific management actions aimed to periodically remove this neglected anthropogenic litter.

Detritus-based assemblage responses under salinity stress conditions in a disused aquatic artificial ecosystem.

BACKGROUND: Despite the plethora of approaches, the sensitivity of the methods to measure the relationship between the abundance and biomass curves in stressed detritus-based ecosystems still remain to be refined. In this work, we report the comparison between biomass and abundance in a set of detritus-based macrozoobenthic assemblages located in six sampling pools with different salinity in an artificial aquatic ecosystem (disused Tarquinia Saltworks), using two diversity/dominance approaches (Abundance/Biomass Comparisons, or ABC, and Whittaker plots). We also evaluated the contribution of abundances and biomasses diversity (Simpson index) and nestedness, which measures the order by which macroinvertebrates colonized the detrital resource. RESULTS: The outputs obtained by both ABC curves and Whittaker plots highlight two different thresholds in assemblage structure: between about 44 and 50 practical salinity unit (psu) and between 50 and 87 psu, respectively. The first threshold was due to a turnover in taxon composition between assemblages, the second threshold (evidenced by Whittaker plots) was due to a change in taxon richness (lower in pools with higher salinity: i.e. > 50 psu). Moreover, a normal-shaped pattern in diversity (Simpson index) emerged, suggestive of an intermediate disturbance effect. The nested pattern did not show significant differences when considering the density and biomass of the sampled taxa, providing similar threshold of salinity in the relative contribution of macrozoobenthos on nestedness. CONCLUSIONS: The use of detailed (ABC and Whittaker plots) and macroscopic (Simpson index and nestedness) approaches is proposed to identify thresholds in the structuring and functioning of detritus-based community of disused aquatic ecosystems: in particular, the inclusion of the parameter of biomass (scarcely utilized in community-based research) appears crucial. The responses of macrozoobenthic assemblages to the salinity stress conditions, in term of abundance and biomass, using a detritus food source (Phragmites australis leaves), may also highlight, by comparing macroscopic and detailed approaches, structuring and functioning patterns to consider for the management of disused artificial ecosystems.

Infaunal macrobenthic community dynamics in a manipulated hyperhaline ecosystem: a long-term study.

BACKGROUND: Understanding the responses of ecological communities to human-induced perturbations is crucial for establishing conservation goals. Ecological communities are dynamic entities undergoing fluctuations due to their intrinsic characteristics as well as anthropogenic pressures varying over time. In this respect, long-term studies, based on large spatial and temporal datasets, may provide useful information in understanding patterns and processes influencing the communities' structure. Theoretical evidence suggests that a role of biodiversity is acting as a compensatory buffer against environmental variability by decreasing the temporal variance in ecosystem functioning and by raising the level of community response to perturbations through the selection of better performing species. Therefore, the spatial and temporal changes in the specialization of the community components may be used as an effective tool to monitor the effects of natural and anthropogenic alterations of the environment in dynamic systems. We examined the temporal dynamics of macroinvertebrate community structure in the hyperhaline habitat of Tarquinia Saltworks (central Italy). We aimed at: (i) investigating the relationships between the level of community specialization and the alterations of the environment across fourteen years; (ii) comparing the ability of aggregate community parameters such as the average abundance vs. species specialization in describing patterns of community composition. RESULTS: We arranged the data in three sub-sets according to three periods, each characterized by different environmental conditions. The mean abundance of sampled macroinvertebrates showed a significant change (p < 0.01) only in the community inhabiting the saltwork basin closely connected to the sea, characterized by the highest environmental variation (i.e. the coefficient of variation, CV, of the aggregate environmental variability over the study period, CVrange = 0.010 - 0.2). Here we found marine species like Modiolus adriaticus (Lamarck, 1819), Neanthes irrorata (Malmgren, 1867), and Amphiglena mediterranea (Leydig, 1851), which inhabited the saltworks during the halt period but disappeared during the subsequent eutrophication phase. Conversely, species specialization showed a significant decrease for each sampled community in the presence of habitat degradation and a recovery after ecological restoration. The widest fluctuations of specialization were recorded for the community inhabiting the saltwork basin with the highest long-term environmental variability. CONCLUSIONS: Recent advances have shown how the increased temporal and spatial variability of species' abundance within the communities may be a signal of habitat disturbance, even in the absence of an apparent decline. Such approach could also be used as a sensitive monitoring tool, able to detect whether or not communities are subjected to increasing biotic homogenization. Also, the increased functional similarity triggered by habitat degradation may impact on species at higher trophic levels, such as the waterbirds wintering in the area or using it as a stopover during migration.