Detection and quantification of benthic litter in selected shallow Maltese coastal areas

Abstract

Despite the protocols imposed at both the European Union (EU) and national levels, the coastal areas around the Maltese islands are still sparsely monitored. For important areas such as marinas, there is still no quantitative data regarding benthic marine litter. The main focus of this work is to identify a good methodology for the monitoring and tabulation of the quantitative abundance as well as categorical composition of benthic marine litter in four specifically selected sites. In particular, the Manoel Island Marina, the Msida Marina, Bugibba Bay, and Spinola Bay were studied. Site selection was based on climatological wind data, level of activity, and logistical access. In total, more than 1.2km of coast was analysed at a high spatial resolution through the use of an imaging system that was deployed at specific locations along the coastline. For each of the four locations, two sets of data were collected in different months. This allowed for a temporal analysis of the quantity and type of litter to be made. All detected objects were classified according to the 24 categories as specified in the Marine Strategy Framework Directive. Msida Marina was found to be the most polluted. 252 and 216 objects were recorded in October 2019 and February 2020 respectively. On the other hand, Bugibba Bay had the least litter items. Here, 68 and 46 objects were detected in the two visits. Spinola Bay contained a total of 111 and 163 objects while Manoel Island Marina contained a total of 112 and 126 objects. Every site was very diverse in terms of the litter found. The most common objects were made of metal, glass, and plastics. The correlation between the identified objects and the bathymetry values at each of these sites, was also investigated.