Marine Protected Area Networks: Assessing Whether the Whole Is Greater than the Sum of Its Parts

Anthropogenic impacts are increasingly affecting the world’s oceans. Networks of marine protected areas (MPAs) provide an option for increasing the ecological and economic benefits often provided by single MPAs. It is vital to empirically assess the effects of MPA networks and to prioritize the monitoring data necessary to explain those effects. We summarize the types of MPA networks based on their intended management outcomes and illustrate a framework for evaluating whether a connectivity network is providing an outcome greater than the sum of individual MPA effects. We use an analysis of an MPA network in Hawai’i to compare networked MPAs to non-networked MPAs to demonstrate results consistent with a network effect. We assert that planning processes for MPA networks should identify their intended outcomes while also employing coupled field monitoring-simulation modeling approaches, a powerful way to prioritize the most relevant monitoring data for empirically assessing MPA network performance

Herbivory, Connectivity, and Ecosystem Resilience: Response of a Coral Reef to a Large-Scale Perturbation

Coral reefs world-wide are threatened by escalating local and global impacts, and some impacted reefs have shifted from coral dominance to a state dominated by macroalgae. Therefore, there is a growing need to understand the processes that affect the capacity of these ecosystems to return to coral dominance following disturbances, including those that prevent the establishment of persistent stands of macroalgae. Unlike many reefs in the Caribbean, over the last several decades, reefs around the Indo-Pacific island of Moorea, French Polynesia have consistently returned to coral dominance following major perturbations without shifting to a macroalgae-dominated state. Here, we present evidence of a rapid increase in populations of herbivorous fishes following the most recent perturbation, and show that grazing by these herbivores has prevented the establishment of macroalgae following near complete loss of coral on offshore reefs. Importantly, we found the positive response of herbivorous fishes to increased benthic primary productivity associated with coral loss was driven largely by parrotfishes that initially recruit to stable nursery habitat within the lagoons before moving to offshore reefs later in life. These results underscore the importance of connectivity between the lagoon and offshore reefs for preventing the establishment of macroalgae following disturbances, and indicate that protecting nearshore nursery habitat of herbivorous fishes is critical for maintaining reef resilience

Food habits of the farmer damselfish Stegastes nigricans inferred by stomach content, stable isotope, and fatty acid composition analyses

The territorial damselfish, Stegastes nigricans, maintains algal farms by excluding invading herbivores and weeding unpalatable algae from its territories. In Okinawa, Japan, S. nigricans farms are exclusively dominated by Polysiphonia sp., a highly digestible filamentous rhodophyte. This study was aimed at determining the diet of S. nigricans in Okinawa and its dependency on these almost-monoculture algal farms based on stomach content and chemical analyses. Stomach content analyses revealed that all available food items in the algal farms (i. e., algae, benthic animal inhabitants, trapped detritus) were contained in fish stomachs, but amorphous organic matter accounted for 68% of the contents. Therefore, carbon and nitrogen stable isotope ratios and fatty acid (FA) compositions were analyzed to trace items actually assimilated in their bodies. Stable isotope analyses showed that benthic animals were an important food source even for this farmer fish. Two essential fatty acids (EFAs), 20:4n6 and 20:5n3, which are produced only by rhodophytes among available food items, were rich in the muscle tissue of S. nigricans as well as in algal mats and detritus, suggesting that algal mats contribute EFAs to S. nigricans directly and indirectly through the food web. In conclusion, S. nigricans ingested algal mats, detritus, and benthic animals maintained within its farm. Algae and detritus were original sources of EFAs, and benthic animals, which were much more abundant in the farms than in outside territories, provided a nitrogen-rich dietary source for the fish

Transferts de matière et d'éléments nutritifs sur les récifs coralliens de l'île de la Réunion par deux herbivores, Tripneustes gratilla (Echinodermata, Echinoidea) et Stegastes nigricans (Pisces, Pomacentridae)

AIX-MARSEILLE2-BU Sci.Luminy (130552106) / SudocPOLYNESIE-BU (987352101) / SudocAIX-MARSEILLE2-Stat.Mar. Endoume (130552206) / SudocSudocFranceF

Variability in the Effects of Macroalgae on the Survival and Growth of Corals: The Consumer Connection

International audienc

Algal food processing by Stegastes nigricans, an herbivorous damselfish: differences between an undisturbed and a disturbed coral reef site (La Reunion, Indian Ocean)

There has, as yet, been little study of nutrient disturbance and its consequences on the functional biology of primary consumers in coral reefs. The processing of epilithic algal communities by the damselfish Stegastes nigricans was investigated at La Reunion, at two sites of a fringing reef, oligotrophic for one and eutrophic for the other. Differences between sites were analyzed in quantifying organic matter, organic carbon, nitrogen, and organic 'nutrients' (carbohydrate, lipid and protein) in the algal food, the digestive contents and the faeces of S. nigricans. In the disturbed site, algal turfs and digestive contents presented significantly higher organic matter, organic carbon, nitrogen and organic nutrient values. Absorption efficiency of total matter was higher in fish from this site (26.8 %) than from the undisturbed site (16.3 %), as well for organic matter, organic carbon, nitrogen and organic nutrients. A larger mean total length was also measured for fish sampled in the disturbed site (11.4 cm versus 10.9 cm). The reinjection of organic nutrients by this herbivorous fish appeared to be enhanced in this site. It is suggested that eutrophication is the main disturbance factor accounting for the recorded differences.L'effet des perturbations trophiques et leurs conséquences sur la biologie fonctionnelle des consommateurs primaires des récifs coralliens a été peu étudié. Cet article présente la transformation des communautés algales épilithiques (gazons algaux) par le poisson demoiselle herbivore Stegastes nigricans, sur un récif frangeant de l'Ile de La Réunion dans deux sites du platier récifal interne : non perturbé et oligotrophe pour l'un, perturbé et eutrophe pour l'autre. Les différences entre les sites ont été analysées en quantifiant les teneurs en matière organique, carbone organique, azote total et ‘nutriments’ (glucides, lipides et protéines), dans la nourriture algale, les contenus digestifs et les fèces de S. nigricans. Dans le site perturbé, les gazons algaux et les contenus digestifs des poissons sont caractérisés par des pourcentages de matière organique et des teneurs en carbone organique, azote total et nutriments significativement plus élevés que dans le site non-perturbé. Les taux d'absorption totaux sont plus élevés chez les poissons de ce site (26,8 %) que chez les poissons du site non-perturbé (16,3 %). Le même résultat est observé pour les taux d'absorption de la matière organique, du carbone organique, de l'azote total et des nutriments. La longueur totale des poissons prélevés est supérieure chez les poissons prélevés sur le site perturbé (11,4 cm contre 10,9 cm). La réinjection de nutriments dans l'écosystème par ce poisson herbivore est plus importante dans ce site. L'eutrophisation semble être le facteur principal qui explique les différences relevées entre les sites