The health of the ocean, central to human well-being, has now reached a critical point. Most fish stocks are overexploited, climate change and increased dissolved carbon dioxide are changing ocean chemistry and disrupting species throughout food webs, and the fundamental capacity of the ocean to regulate the climate has been altered. However, key technical, organizational, and conceptual scientific barriers have prevented the identification of policy levers for sustainability and transformative action. Here, we recommend key strategies to address these challenges, including (1) stronger integration of sciences and (2) ocean-observing systems, (3) improved science-policy interfaces, (4) new partnerships supported by (5) a new ocean-climate finance system, and (6) improved ocean literacy and education to modify social norms and behaviors. Adopting these strategies could help establish ocean science as a key foundation of broader sustainability transformations.
amalgamates the top-down and bottom-up approaches to BE management. Achieving the goal of successful blue growth in Africa is now even more challenged by the implications of COVID-19 on the BE sectors. Reimagining and rebuilding a resilient BE in Africa post-coronavirus will require a strong political commitment to promoting a balance between economic, social and environmental benefits in line with the African Union's Agenda 2063 and the United Nations' Sustainable Development Goals.
Prokaryotic epiphytes on leaves of three seagrass species, Thalassodendron ciliatum, Thalassia hemprichii, and Cymodocea rotundata, from two Kenyan coastal sites, Nyali (a high-nutrient site) and Vipingo (a lownutrient site), were characterized genetically and morphologically. Denaturing gradient gel electrophoresis (DGGE) and clone libraries of PCRamplified 16S rRNA gene fragments were used to study prokaryotes associated with these seagrasses. In general, the epiphytic coverage was greater in the high-nutrient site, while the microbial diversity was linked to seagrass species rather than the study sites. Cytophaga-Flavobacteria-Bacteroides (CFB) were associated with T. ciliatum and T. hemprichii mainly in the nutrient-poor site, while a-, b-, and c-proteobacteria were associated with all three species at the two study sites. Some bacteria phylotypes were closely related to sequences of microorganisms previously recovered from wastewaters or other contaminated sources, indicating the influx of landbased wastes into these coastal lagoon ecosystems. The abundance of potential nitrogen (N 2 )-fixing cyanobacteria on C. rotundata, particularly in the low-nutrient site, suggested that this association may have been acquired to meet N demands. Unicellular cyanobacteria were dominant and associated with C. rotundata and T. hemprichii (with those on T. hemprichii being closely related to cyanobacterial symbiotic species), while T. ciliatum was almost devoid of cyanobacterial associations at the same site (Nyali), which suggests specificity in the cyanobacteria-seagrass associations. The abundance of prokaryotic epiphytes was considered to be linked to water depth and tidal exposure.
The aim of the present study was to investigate lvhether trop~cal intertidal seagrasses were better adapted to tolerate des~ccatlon than subt~dally growing seagrasses To do t h~s , the photosynthetic performance of 8 seagrass species, gro1nng from the upper intertidal to the shallow s u b t~d a l m Zanzibar East Africa was studied during the event of air exposure and the subsequent rehydration Photosynthet~c eff~ciencies were measured by pulse amplitude modulated (PAM) fluorometry as effective electron quantum y~e l d s of photosystem I1 (Y) since it had recently been shown that t h~s measure parallels rates of O2 evolutlon tor several specles under a d e f~n e d ~r r a d~a n c e Contrary to our expectabons it was found that the shallow intertidal specles wele in genelal more sensitive to desiccation than the deeper species Thls was expressed both as a faster decllne In Y at decreasing water contents and as an l n a b~l~t y to regain full photosynthetic rates d u r~n g reh\ dratlon follow~ng even mild d e s~c c a t~o n as compared with the deeper-glowing speclcs One exception was the subtldally growlng S y n n g o d~u m ~soetlfoiium, w h~c h was very sensitive to deslccatlon The 2 specles whlch grow highest up in the Intert~d a l zone Haioph~ia ovalis and Halodule wnghtu may not desiccate much in s~t u during low tide because the leaves lie flat on the molst sand and for the latter specles, overlap one another so as to m n l m s e water loss Thus ~t seems that d e s~c c a t~o n tolerance is not a trait whlch determnes the vertical zonatlon of trop~cal seagrasses Rather, it IS hypothesised that the ablllty to t o l e~a t e h~g h ~~r a d~a n c e s , as well as to benefit from h~g h nutnent lnputs f~o r n the shore, allows the shallow specles to occupy the uppermost lntert~dal zone KEY WORDS Desiccat~on . PAM fluorometry Photosynthes~s Seagrass . Tropical
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