Functional metagenomic insights into a freshwater lake Mgobezeleni affected by harmful cyanobacterial bloom

Cyanobacterial harmful algal blooms (CHABs) are a major threat to freshwater ecosystems globally that are primarily driven by human activities. Anthropogenic impacts associated with urban, agricultural and industrial activity near freshwater systems lead to the eutrophication, which favours the growth of dominant CHABs in both the planktonic and benthic habitats. Lake Mgobezeleni, located in the Northern Maputaland region of KwaZulu Natal province in South Africa, has experienced algal blooms attributed to ground water contamination from the surrounding areas. Northern Maputaland region in KwaZulu-Natal province consists of many water bodies including freshwater lakes (Mgobezeleni, Sibaya, Shazibe and St Lucia) and one of the South Africa’s largest estuarine system (Lake St Lucia) that are important habitats for many endemic species in northeastern South Africa. In the present study, the samples were collected at two different seasons from the fresh water lakes of Maputaland system. The first set of sample was collected during last week of spring season (November 24th, 2015) from Lake Mgobezeleni, during an algal bloom. The second set of samples were collected during the summer season (January 26th 2016) from Lake Mgobezeleni and its associated estuary as well as Lake Sibaya and Lake Shazibe. In this study we have employed shotgun metagenomics together with 16S rRNA gene amplicon sequencing to provide better resolution of the cyanobacterial taxonomy at the species level and used functional genomics to investigate the potential for cyanotoxin production in Lake Mgobezeleni.