Extended study on floating litter in Malta's coastal waters (Central Mediterranean).

This study aims to determine the level of floating marine litter in coastal and inshore areas around Malta and Gozo (Central Mediterranean) and to investigate factors which influence litter distribution. Observations of macro-litter and mega-litter were conducted through seasonal boat surveys around Malta and Gozo during 2018-2019. Visual observations were conducted along line transects whilst maintaining a 6 m observation width. For coastal areas, of up to -1 km away from the shoreline, the total density of litter ranged between 27 and 2428 items/km2, with a mean of 292 ± 85 items/km2. Within inshore areas the density varied between 180 and 46,289 items/km2, with a mean of 3242 ± 1880 items/km2. The highest density was present in winter, this being 2.5 higher than the lowest density season. 91% of the litter was plastic. The manner in which anthropogenic factors and natural events influenced litter accumulations and distributions, are described.

Sewage pollution impact on Mediterranean rocky-reef fish assemblages.

The effects of sewage outfalls on subtidal fish assemblages were studied along the NW coasts of Malta (Sicily channel, Mediterranean Sea) by means of underwater visual census. The presence of two spatially distinct outfalls discharging untreated wastewaters allowed to use a balanced symmetrical after control/impact (ACI) design that consisted of two putatively impacted locations and two controls, with four sites nested in each location. Surveys were performed in 2006 at two random dates. The study highlighted significant changes at both assemblage and individual species levels. Fish assemblages structures were different between controls and sewages, where total abundance of fish were higher. The responses of individual species to sewage pollution were mostly related to an anomalous increase of two small opportunistic species i.e. Gobius bucchichii and Parablennius rouxi and to a decrease of species of the genus Symphodus, particularly S. roissali and S. ocellatus. Moreover in correspondence of the outfalls, significant changes of the fish size distribution were detected for several species. These results support the use of fish assemblages as biological indicators for marine coastal waters and demonstrated the possibility to obtain sharp signals of environmental impact from some individual fish species.

Imposex as a biomonitoring tool for marine pollution by tributyltin: some further observations.

Imposex, i.e., the imposition of male sexual characteristics on female neograstropods, has been used worldwide as a bioindicator of pollution by the antifouling agent TBT as well as to assess the related ecological impact. The recent total ban on the use of TBT in the maritime industry has been partly based on the use of such a biomarker. This is mainly based on the assumption that no other pollutant, or environmental stress, is able to induce such a biological response. Nonetheless, several authors had challenged this idea. The present paper will present further field observations on imposex in Hexaplex trunculus from Malta (Central Mediterranean) which may help clarify this issue. Furthermore, the incidence of imposex in this species will be related to body burdens and to the environmental levels of organotins as measured analytically. First histological observations will also be presented which may help clarify the ecological significance of this response in this species. Finally a number of alternative scenarios regarding the relationship between imposex and TBT will be discussed.