Environmental variability indicates a climate‐adaptive center under threat in northern Mozambique coral reefs

Abstract

Abstract. A priority for modern conservation is finding and managing regions with environmental and biodiversity portfolio characteristics that will promote adaptation and the persistence of species during times of rapid climate change. The latitudinal edges of high-diversity biomes are likely to provide a mixture of environmental gradients and biological diversity that meet the portfolio criteria needed for adaptive systems. Northern Mozambique and the Quirimbas Islands represent the edge of a coral reef diversity center with limited potential to expand because of geologic and oceanographic limits on the southern edges. This region does, however, have the potential to be its own discrete adaptive center if it contains climate refugia and there are environmental gradients that promote acclimatization, ecological reorganization, and natural selection. Consequently, to evaluate this potential we tested for strong regional environmental spatial heterogeneity that might indicate a climate-adaptive center. Additionally, we evaluated human influences and environmental and demographic data on finfish, coral, and sea urchins in 66 reefs across~4°of latitude to evaluate ecological changes and human threats. A number of clear gradients in environmental and human influences were observed. For example, temperature increased and became more centralized and right-skewed, while water quality decreased to the south. Coral communities susceptible to thermal stress were found in the north where dispersed temperatures indicated a location with either tolerance to or refugium from recent thermal disturbances. Nevertheless, high coral diversity was found in southern deep-water channels. Further, spatial patterns for corals and fish differed indicating complex geographicfishing-biodiversity gradients. Consequently, environmental conditions for an adaptive portfolio exist and include refugia for preserving climate-sensitive and for numbers of coral taxa. Fishing and urban threats were observable as reduced fish biomass, diversity, and body sizes but higher biomass of sea urchins. We observed that many remote and protected areas had fish biomass values lower than expected or near maximum sustainable yields. This indicates low compliance and widespread migratory fishing, which is reducing fish diversity below maximum levels. Recommendations to sustain this adaptive center are to maintain fish biomass >500 kg/ha by increasing fisheries restrictions and compliance.

Managing coral reef fish community biomass is a priority for biodiversity conservation in Madagascar

“…Biomasses in the high human influence areas were composed of taxa of low fisheries or economic value, including small damselfish and odd-shaped piscivores such as lizardfish, cornetfish, scorpionfish, and trumpetfish. Human influence and related variables have been shown to be good predicators of fish biomass and vulnerable taxa in some regions (Brewer et al 2013, Maire et al 2016) but such variables may be a crude metric of human impacts because of variations in the responses of target and non-target taxa and whether or not fishers are migratory (McClanahan & Muthiga 2017). The human influence metric does not take account of resource abundance metrics, such as reef area, nor of human infrastructure and travel time, or livelihood alternatives such as agriculture and animal husbandry among other socioeconomic attributes that should influence fishing pressure .…”

Applying a Social–Ecological Systems Approach to Understanding Local Marine Management Trajectories in Northern Mozambique

“…The villages vary in population size, between 537 (Nsangue Ponta) and 3408 (Malinde). Cabo Delgado is home to a variety of coastal and marine habitats, including large and diverse areas of coral reefs [44,45] which have demonstrated a regionally high level of ecological resilience to coral bleaching [46]. Poverty affects 44.8% of the Cabo Delgado population [47] and most rural areas are poorly served by basic public services and infrastructure.…”

Coral Reef Conservation Solution-Scape White Paper

“…With recurrent mass bleaching as a result of climate-change-induced ocean warming (Hughes et al 2017b) and potentially limited windows for slow-growing corals to recover (Côté and Darling 2010), what new tools and interventions are needed to ensure that reef conservation interventions are climate smart? There are two positive aspects to the responses of corals to raised water temperatures: first, there is increasing evidence that not all coral species or locations bleach equally (McClanahan et al 2007, McClanahan et al 2011a, Darling et al 2013, Hughes et al 2017b, McClanahan and Muthiga 2017, and second, surviving corals can, in some contexts, adapt to repeated bleaching events (Guest et al 2012, Howells et al 2012, McClanahan 2017. Climatesmart conservation can leverage these diverse responses and use a variety of management strategies and technical tools that would allow "nature to pick the winners" in any particular location (Webster et al 2017).…”

“…• Known "climate refuges"-places where slow-growing corals are known either to be able adapt to ocean warming or not exposed to it-can be protected and carefully managed. These locations may include access to deeper reefs and channels, shallow lagoons that have long been exposed to variable temperatures and where corals continue to survive, and areas of cool-water upwelling driven by gyres or eddies (Oliver and Palumbi 2011, Ainsworth et al 2016, McClanahan and Muthiga 2017. Reefs that experience chronic and acute thermal exposure over time may be critically important for maintaining a diversity of species that are capable of resistance and recovery (Mumby et al 2011, Webster et al 2017).…”