The important role of marine debris networks to prevent and reduce ocean plastic pollution.

Societal change is needed to prevent and reduce the growth in the amount of solid waste entering the sea. Marine debris networks cover a broad range of activities in order to protect our oceans. By following a common vision and a collective systematic approach they are capable of creating synergies between all relevant stakeholders that result in reducing the flow of waste into our oceans. Thus, they are key to achieving the Sustainable Development Goals. During the 6th International Marine Debris Conference in San Diego in 2018, different marine debris networks from different parts of the world presented their activities, achievements and challenges. This led to network representatives agreeing to collaborate as members of an International Waste Platform. This platform aims to harmonize objectives, share knowledge, join forces and help new networks to emerge.

DNA profiling of Tilapia guinasana, a species endemic to a single sinkhole, to determine the genetic divergence between color forms.

Northwestern South Africa and Namibia contain a number of sinkholes in the dolomitic rock formations found in this area. These contain isolated populations of Tilapia. Most contain Tilapia sparmanii, but the one in Namibia, Guinas, is of particular interest as it contains the endemic species, Tilapia guinasana, which exhibits none sex-limited polychromatisms, which is unique for Tilapia. This sinkhole is under environmental threat, particularly as a result of being a recreational diving site. This study, using randomly amplified polymorphic DNA sequences (RAPDs), when analyzed using analysis of variance (ANOVA), shows that the colour forms of Tilapia guinasana are genetically distinct. This confirms previous evidence that assortative mating between color forms takes place. The various possible hypotheses for the occurrence and genetic stability of the color polymorphism are discussed. Further, a new hypothesis is put forward based on a need to maximize outbreeding in fully isolated population with no possibility of increase in size above the maximum and limited carrying capacity of the sinkhole.