Brilliantia kiribatiensis, a new genus and species of Cladophorales (Chlorophyta) from the remote coral reefs of the Southern Line Islands, Pacific Ocean.

The marine green alga Brilliantia kiribatiensis gen. et sp. nov. is described from samples collected from the coral reefs of the Southern Line Islands, Republic of Kiribati, Pacific Ocean. Phylogenetic analysis of sequences of the large- and small-subunit rDNA and the rDNA internal transcribed spacer region revealed that Brilliantia is a member of the Boodleaceae (Cladophorales), containing the genera Apjohnia, Boodlea, Cladophoropsis, Chamaedoris, Phyllodictyon, and Struvea. Within this clade it formed a distinct lineage, sister to Struvea elegans, but more distantly related to the bona fide Struvea species (including the type S. plumosa). Brilliantia differs from the other genera by having a very simple architecture forming upright, unbranched, single-celled filaments attached to the substratum by a rhizoidal mat. Cell division occurs by segregative cell division only at the onset of reproduction. Based on current sample collection, B. kiribatiensis seems to be largely restricted to the Southern Line Islands, although it was also observed on neighboring islands, including Orona Atoll in the Phoenix Islands of Kiribati, and the Rangiroa and Takapoto Atolls in the Tuamotus of French Polynesia. This discovery highlights the likeliness that there is still much biodiversity yet to be discovered from these remote and pristine reefs of the central Pacific.

Ecophysiology of coral reef primary producers across an upwelling gradient in the tropical central Pacific.

Upwelling is an important source of inorganic nutrients in marine systems, yet little is known about how gradients in upwelling affect primary producers on coral reefs. The Southern Line Islands span a natural gradient of inorganic nutrient concentrations across the equatorial upwelling region in the central Pacific. We used this gradient to test the hypothesis that benthic autotroph ecophysiology is enhanced on nutrient-enriched reefs. We measured metabolism and photophysiology of common benthic taxa, including the algae Porolithon, Avrainvillea, and Halimeda, and the corals Pocillopora and Montipora. We found that temperature (27.2-28.7°C) was inversely related to dissolved inorganic nitrogen (0.46-4.63 µM) and surface chlorophyll a concentrations (0.108-0.147 mg m-3), which increased near the equator. Contrary to our prediction, ecophysiology did not consistently track these patterns in all taxa. Though metabolic rates were generally variable, Porolithon and Avrainvillea photosynthesis was highest at the most productive and equatorial island (northernmost). Porolithon photosynthetic rates also generally increased with proximity to the equator. Photophysiology (maximum quantum yield) increased near the equator and was highest at northern islands in all taxa. Photosynthetic pigments also were variable, but chlorophyll a and carotenoids in Avrainvillea and Montipora were highest at the northern islands. Phycobilin pigments of Porolithon responded most consistently across the upwelling gradient, with higher phycoerythrin concentrations closer to the equator. Our findings demonstrate that the effects of in situ nutrient enrichment on benthic autotrophs may be more complex than laboratory experiments indicate. While upwelling is an important feature in some reef ecosystems, ancillary factors may regulate the associated consequences of nutrient enrichment on benthic reef organisms.

Environmental impacts and implications of tropical carrageenophyte seaweed farming.

Field-based cultivation of Kappaphycus and Eucheuma seaweeds is widespread across the tropics and is largely done to extract the polysaccharide carrageenan, which is used in commercial applications. Although such seaweed farming has been cited as a sustainable alternative livelihood to destructive fishing, there has not been a comprehensive review of its environmental impacts to assess its potential conservation benefit. We reviewed the peer-reviewed and industry gray literature to determine what is known about seaweed farming techniques and their impacts on local ecosystems, organisms, and ecosystem services. We identified 43 tropical or subtropical countries that are currently cultivating or have cultivated carrageenophytes. Ecosystem impacts of seaweed farming were measured directly in 33 publications with variable results. Placement of seaweed farms above seagrass beds led to reduced productivity and shoot density in 5 studies and reduced or altered meiofaunal abundance and diversity in 6 studies. On coral reefs, overgrowth of corals by farmed seaweed species was documented in 8 cases. Two studies showed changes to herbivorous fish communities in adjacent areas because seaweed farms changed the environment, whereas in 2 studies measures of overall abundance or diversity did not change. The impacts of seaweed farming may not be as destructive as some other human activities, but they should still be considered when establishing new farms or managing existing farm sites. Our findings are consistent with suggestions to mitigate impact on local ecosystems by shifting seaweed farms to deeper, sandy-bottom areas. However, some of these changes may adversely affect farmers and associated communities.

Impactos e Implicaciones Ambientales del Cultivo de Algas Marinas Carragenofitas Tropicales Resumen El cultivo de las algas marinas Kappaphycus y Eucheuma se encuentra distribuido extensamente en los trópicos y generalmente se realiza para extraer el polisacárido carragenano, el cual se usa en la industria comercial. Aunque se ha mencionado que dicho cultivo de algas marinas es una alternativa sustentable para la pesca destructiva como medio de subsistencia, no se ha realizado una revisión completa de sus impactos ambientales para evaluar su potencial beneficio de conservación. Analizamos la literatura gris y la revisada por pares sobre la industria para determinar qué se conoce sobre las técnicas de cultivo de algas marinas y sus impactos sobre los ecosistemas locales, organismos y servicios ambientales. Identificamos 43 países tropicales o subtropicales que actualmente cultivan o han cultivado carragenofitas. Medimos los impactos ambientales del cultivo de algas marinas de manera directa en 33 publicaciones con resultados variables. La colocación de granjas de algas marinas por encima de lechos de pasto marino derivó en una productividad reducida y en una densidad observada en cinco estudios. En seis estudios, esta colocación derivó en una reducción o alteración de la abundancia y diversidad de meiofauna. En los arrecifes de coral, se documentó en ocho casos la proliferación de corales por causa de las especies cultivadas de algas marinas. Dos estudios mostraron cambios en las comunidades de peces herbívoros de las áreas circundantes debido al cambio en el ambiente generado por los cultivos de algas marinas, mientras que, en otros dos estudios, las medidas de la abundancia o diversidad generalizadas no cambió. Los impactos del cultivo de algas marinas pueden no ser tan destructivos como otras actividades humanas, pero todavía deberían considerarse durante el establecimiento de nuevas granjas o durante el manejo de los sitios de cultivo existentes. Nuestros hallazgos van a la par de las sugerencias actuales para mitigar el impacto sobre los ecosistemas locales mediante la reubicación de las granjas de algas marinas a áreas más profundas con un lecho arenoso. Sin embargo, algunos de estos cambios podrían afectar negativamente a los cultivadores y a las comunidades asociadas.

Diel population and functional synchrony of microbial communities on coral reefs.

On coral reefs, microorganisms are essential for recycling nutrients to primary producers through the remineralization of benthic-derived organic matter. Diel investigations of reef processes are required to holistically understand the functional roles of microbial players in these ecosystems. Here we report a metagenomic analysis characterizing microbial communities in the water column overlying 16 remote forereef sites over a diel cycle. Our results show that microbial community composition is more dissimilar between day and night samples collected from the same site than between day or night samples collected across geographically distant reefs. Diel community differentiation is largely driven by the flux of Psychrobacter sp., which is two-orders of magnitude more abundant during the day. Nighttime communities are enriched with species of Roseobacter, Halomonas, and Alteromonas encoding a greater variety of pathways for carbohydrate catabolism, further illustrating temporal patterns of energetic provisioning between different marine microbes. Dynamic diel fluctuations of microbial populations could also support the efficient trophic transfer of energy posited in coral reef food webs.

Gradients in Primary Production Predict Trophic Strategies of Mixotrophic Corals across Spatial Scales.

Mixotrophy is among the most successful nutritional strategies in terrestrial and marine ecosystems. The ability of organisms to supplement primary nutritional modes along continua of autotrophy and heterotrophy fosters trophic flexibility that can sustain metabolic demands under variable or stressful conditions. Symbiotic, reef-building corals are among the most broadly distributed and ecologically important mixotrophs, yet we lack a basic understanding of how they modify their use of autotrophy and heterotrophy across gradients of food availability. Here, we evaluate how one coral species, Pocillopora meandrina, supplements autotrophic nutrition through heterotrophy within an archipelago and test whether this pattern holds across species globally. Using stable isotope analysis (δ13C) and satellite-derived estimates of nearshore primary production (chlorophyll-a, as a proxy for food availability), we show that P. meandrina incorporates a greater proportion of carbon via heterotrophy when more food is available across five central Pacific islands. We then show that this pattern is consistent globally using data from 15 coral species across 16 locations spanning the Caribbean Sea and the Indian and Pacific Oceans. Globally, surface chlorophyll-a explains 77% of the variation in coral heterotrophic nutrition, 86% for one genus across 10 islands, and 94% when controlling for coral taxonomy within archipelagos. These results demonstrate, for the first time, that satellite-derived estimates of nearshore primary production provide a globally relevant proxy for resource availability that can explain variation in coral trophic ecology. Thus, our model provides a pivotal step toward resolving the biophysical couplings between mixotrophic organisms and spatial patterns of resource availability in the coastal oceans.

Investigating functional redundancy versus complementarity in Hawaiian herbivorous coral reef fishes.

Patterns of species resource use provide insight into the functional roles of species and thus their ecological significance within a community. The functional role of herbivorous fishes on coral reefs has been defined through a variety of methods, but from a grazing perspective, less is known about the species-specific preferences of herbivores on different groups of reef algae and the extent of dietary overlap across an herbivore community. Here, we quantified patterns of redundancy and complementarity in a highly diverse community of herbivores at a reef on Maui, Hawaii, USA. First, we tracked fish foraging behavior in situ to record bite rate and type of substrate bitten. Second, we examined gut contents of select herbivorous fishes to determine consumption at a finer scale. Finally, we placed foraging behavior in the context of resource availability to determine how fish selected substrate type. All species predominantly (73-100 %) foraged on turf algae, though there were differences among the types of macroalgae and other substrates bitten. Increased resolution via gut content analysis showed the composition of turf algae consumed by fishes differed across herbivore species. Consideration of foraging behavior by substrate availability revealed 50 % of herbivores selected for turf as opposed to other substrate types, but overall, there were variable foraging portfolios across all species. Through these three methods of investigation, we found higher complementarity among herbivorous fishes than would be revealed using a single metric. These results suggest differences across species in the herbivore "rain of bites" that graze and shape benthic community composition.

Responses of Herbivorous Fishes and Benthos to 6 Years of Protection at the Kahekili Herbivore Fisheries Management Area, Maui.

In response to concerns about declining coral cover and recurring macroalgal blooms, in 2009 the State of Hawaii established the Kahekili Herbivore Fisheries Management Area (KHFMA). Within the KHFMA, herbivorous fishes and sea urchins are protected, but other fishing is allowed. As part of a multi-agency monitoring effort, we conducted surveys at KHFMA and comparison sites around Maui starting 19 months before closure, and over the six years since implementation of herbivore protection. Mean parrotfish and surgeonfish biomass both increased within the KHFMA (by 139% [95%QR (quantile range): 98-181%] and 28% [95%QR: 3-52%] respectively). Most of those gains were of small-to-medium sized species, whereas large-bodied species have not recovered, likely due to low levels of poaching on what are preferred fishery targets in Hawaii. Nevertheless, coincident with greater biomass of herbivores within the KHFMA, cover of crustose coralline algae (CCA) has increased from ~2% before closure to ~ 15% in 2015, and macroalgal cover has remained low throughout the monitoring period. Strong evidence that changes in the KHFMA were a consequence of herbivore management are that (i) there were no changes in biomass of unprotected fish families within the KHFMA; and that (ii) there were no similar changes in parrotfish or CCA at comparison sites around Maui. It is not yet clear how effective herbivore protection might eventually be for the KHFMA's ultimate goal of coral recovery. Coral cover declined over the first few years of surveys-from 39.6% (SE 1.4%) in 2008, to 32.9% (SE 0.8%) in 2012, with almost all of that loss occurring by 2010 (1 year after closure), i.e. before meaningful herbivore recovery had occurred. Coral cover subsequently stabilized and may have slightly increased from 2012 through early 2015. However, a region-wide bleaching event in 2015 had already led to some coral mortality by the time surveys were conducted in late 2015, at which time cover had dropped back to levels recorded in the KHFMA in 2012.

Underwater microscopy for in situ studies of benthic ecosystems.

Microscopic-scale processes significantly influence benthic marine ecosystems such as coral reefs and kelp forests. Due to the ocean's complex and dynamic nature, it is most informative to study these processes in the natural environment yet it is inherently difficult. Here we present a system capable of non-invasively imaging seafloor environments and organisms in situ at nearly micrometre resolution. We overcome the challenges of underwater microscopy through the use of a long working distance microscopic objective, an electrically tunable lens and focused reflectance illumination. The diver-deployed instrument permits studies of both spatial and temporal processes such as the algal colonization and overgrowth of bleaching corals, as well as coral polyp behaviour and interspecific competition. By enabling in situ observations at previously unattainable scales, this instrument can provide important new insights into micro-scale processes in benthic ecosystems that shape observed patterns at much larger scales.