Nutrition from aquatic food diversityHere we reframe the role of aquatic foods in global food systems as a highly diverse food group, which can supply critical nutrients [1][2][3]13

Global climate change is altering community composition across many ecosystems due to nonrandom species turnover, typically characterized by the loss of specialist species and increasing similarity of biological communities across spatial scales. As anthropogenic disturbances continue to alter species composition globally, there is a growing need to identify how species responses influence the establishment of distinct assemblages, such that management actions may be appropriately assigned. Here, we use trait-based analyses to compare temporal changes in five complementary indices of reef fish assemblage structure among six taxonomically distinct coral reef habitats exposed to a system-wide thermal stress event. Our results revealed increased taxonomic and functional similarity of previously distinct reef fish assemblages following mass coral bleaching, with changes characterized by subtle, but significant, shifts toward predominance of small-bodied, algal-farming habitat generalists. Furthermore, while the taxonomic or functional richness of fish assemblages did not change across all habitats, an increase in functional originality indicated an overall loss of functional redundancy. We also found that prebleaching coral composition better predicted changes in fish assemblage structure than the magnitude of coral loss. These results emphasize how measures of alpha diversity can mask important changes in the structure and functioning of ecosystems as assemblages reorganize. Our findings also highlight the role of coral species composition in structuring communities and influencing the diversity of responses of reef fishes to disturbance. As new coral species configurations emerge, their desirability will hinge upon the composition of associated species and their capacity to maintain key ecological processes in spite of ongoing disturbances.

The unfolding COVID-19 pandemic has exposed the vulnerability of the Pacific food system to externalities and has had farreaching impacts, despite the small number of COVID-19 cases recorded thus far. Measures adopted to mitigate risk from the pandemic have had severe impacts on tourism, remittances, and international trade, among other aspects of the political economy of the region, and are thus impacting on food systems, food security and livelihoods. Of particular concern will be the interplay between loss of incomes and the availability and affordability of local and imported foods. In this paper, we examine some of the key pathways of impact on food systems, and identify opportunities to strengthen Pacific food systems during these challenging times. The great diversity among Pacific Island Countries and Territories in their economies, societies, and agricultural potential will be an important guide to planning interventions and developing scenarios of alternative futures. Bolstering regional production and intraregional trade in a currently import-dependent region could strengthen the regional economy, and provide the health benefits of consuming locally produced and harvested fresh foodsas well as decreasing reliance on global supply chains. However, significant production, processing, and storage challenges remain and would need to be consistently overcome to influence a move away from shelf-stable foods, particularly during periods when human movement is restricted and during post-disaster recovery.

A major goal of ecology is to explain the mechanisms that drive species distributions and ecological partitioning along gradients in the natural environment. The distributions of ecologically similar animals may depend on the degree of habitat specialization and behavioural interactions within and among species. The extent of ecological partitioning in guilds of coral reef fishes has been a matter of debate, but the roles of habitat selectivity and agonistic interactions have received little attention. Here these effects were examined by investigating fine-scale species distributions, microhabitat use, and aggression in a guild of 7 territorial damselfish species in Kimbe Bay, Papua New Guinea. We documented patterns of habitat partitioning across the 3 reef zones-reef flat, reef crest, and reef slope-with distinct patterns of distribution within these zones at extremely fine scales (1−2 m). Distinct differences between neighbouring species in the substrata selected were also observed. We hypothesized that fine-scale differences in distribution and microhabitat use could be maintained by aggressive interactions. To test this, we employed a 'bottle' experiment, where stimulus fish were introduced into a resident's territory, and aggression was recorded. Aggression elicited by neighbouring species was significantly higher for all species, compared with non-adjacent species. Levels of aggression differed among species, with the most aggressive species dominating the reef crest where the most distributional overlap occurred. This study revealed a fine level of spatial partitioning among reef zones and microhabitats in this guild of damselfish, which is likely to be maintained by agonistic interactions among neighbouring species. We demonstrate that when exploring coexistence in reef fish communities, the more traditional niche mechanisms operate alongside competitive dynamics, and within highly diverse systems these ecological processes are magnified.

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This is an open access article under the terms of the Creat ive Commo ns Attri bution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

Overfishing of urchin predators, in combination with natural disturbances, has been linked to an increase in the occurrence of urchin barrens. Marine reserves have been proposed as a means to re-establish the interactions between urchins and their predators in California kelp forests. Whether increased densities of lobsters and other predators in reserves are sufficient to convert barrens back to kelp forests depends on the degree to which predators avoid urchins from barren habitats. Urchins from these barrens may be less appealing to predators due to their diminished gonad production and thus decreased quality. In this study, we compared consumption rates of California spiny lobster Panulirus interruptus on purple urchins Strongylocentrotus purpuratus that were collected from kelp forests or from urchin barrens. All size classes of lobster prefer urchins from kelp forests relative to those from barrens and will actively select kelp-bed urchins when given a choice. Lobsters also showed higher consumption rates of kelp-bed urchins when either kelp-bed or barren urchins were presented alone. The large size class of lobsters consumed more and larger urchins than did smaller size classes of lobsters. These results suggest a potential mechanism for the persistence of urchin barrens despite high lobster densities and indicate that lobster foraging preferences may delay phase shifts from barrens back to kelp forests. The results also suggest that preferential foraging by lobsters on kelp-bed urchins may increase the resistance of kelp-beds to changes in state.

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