Congratulations to two successful master thesis presentations

Two master students finished their projects in Dec 2020:

Calum Young: Examination of plankton communities, invaders and harmful algal species within mangrove areas of the Galápagos Islands using eDNA metabarcoding

Phytoplankton are critical components of the marine environment but their understanding within the Galápagos Marine Reserve (GMR) remains largely underexplored with research focused within mangrove systems being further limited. Between November and December, the Galápagos Islands transition from the dry, milder season to the wet, warmer season. By examining the dominant phytoplankton genera within mangrove communities during this time, inference can be made on the communities’ responsiveness to seasonal change. This study utilised environmental DNA (eDNA) metabarcoding of the 18S ribosomal RNA (rRNA) molecular marker to survey the micro-eukaryotic community in surface waters collected from six mangrove sites. Compositions were shown to be influenced by both spatial conditions and seasonality. Diatoms represented a significant proportion of the community and were shown to undergo a strong seasonal shift to dominance by smaller sized taxa, possibly due to their efficient nutrient acquisitional traits. Dominance within dinoflagellates appeared dependent on several eco-physiological strategies; with parasitism and endosymbiosis appearing most advantageous for community dominance. 

Mangrove communities were also examined for invasive and toxic algae species. These groups represent an area of growing concern within the region and exploration of their distribution within the GMR has not previously been conducted using metabarcode sequencing. Here, several new observations of invasive species for the GMR are reported. Additionally, a range of toxin-producing algal species was also detected. However, for both groups, the respective relative abundance of individual species within mangroves communities was minimal. Sites located closer to human activity did not appear to be more impacted by problem species than more isolated areas. The low proportion held by harmful groups is encouraging, but the diversity of species detected warrants improved monitoring to ensure populations and their associated negative impacts remain negligible. 

Vivien Holub: Connectivity through larval dispersal in Kenya and Tanzania: A hydrodynamic connectivity model of marine protected areas   

Marine protected areas (MPAs) are considered as major conservation tools and have been implemented globally to protect marine biodiversity and to support the sustainability of coastal fisheries. Following scientific guidelines, conservation efforts also aim to establish representative MPA networks at various spatial scale, which is expected to enhance the efficiency of individual areas. Yet, degree at which MPA populations are potentially connected by the dispersal of marine organisms remain largely unknown. To address this knowledge gap, the present study investigates connectivity patterns among Kenyan and Tanzanian MPAs (between 0  – 10  and 38 – 47 ) in the Western Indian Ocean, a region where food and livelihood security are highly dependent on coastal fisheries. Interconnectedness is evaluated through a hydrodynamic larval dispersal model parameterized for the seagrass parrotfish Leptoscarus vaigiensis, a heavily targeted fish species by small-scale fisheries in the region. Applying graph theory and various connectivity metrics, this study shows that the Kenyan-Tanzanian MPAs form a weakly connected network where connections are the strongest in the Tanzanian Tanga and Zanzibar region and weakest in the northmost Kenyan MPAs. Poor coherency is likely the result of the predominantly northwardly flow of the regional East African Coastal Current which generates and imbalance of larval migration rate between MPAs on a latitudinal scale. Although connectivity patterns are significantly stronger when the dominant current is temporarily weakened and deflected in North Kenya during NEM season, on average the strength of connectivity remains low. Therefore, the present investigation demonstrates that the regional hydrodynamic patterns poses a challenge for achieving effective MPA network. Continued studies with more conservative model conditions is recommended. However, based on its findings, this study suggest that local governments further increase MPA surface coverage and consider a cross-boundary management of MPAs to improve connectivity.   

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