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  • 1.
    Hellström, Ann Micaela
    et al.
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Benzie, J. A. H.
    Robustness of size measurements in soft corals2011In: Coral reefs (Print), ISSN 0722-4028, E-ISSN 1432-0975, Vol. 30, no 3, p. 787-790Article in journal (Refereed)
    Abstract [en]

    Accurate colony size measurement in soft-bodied sessile aquatic invertebrates is more difficult than in hard corals because of the variable state of the hydroskeleton in the former. The present study examined variation in colony height, oral disc diameter and basal circumference in three species of soft coral of different morphological types (Sarcophyton elegans, Sinularia flexibilis and Dendronephthya sp.) over a 24-h period. Individual colonies changed considerably in size over this period. Coefficients of variation for height measurements and oral disc were 0.09–0.36 and 0.08–0.28, respectively, but were only 0.02–0.09 for basal circumference, in all three species. Measurements of basal circumference in the field showed the highest correlation with colony biomass (volume after water displacement in formalin) confirming basal circumference to be a sound measure of colony size in repeated measurement studies.

  • 2.
    Lokrantz, Jerker
    et al.
    Stockholm University, Faculty of Science, Department of Systems Ecology. Stockholm University, Stockholm Resilience Centre.
    Nyström, Magnus
    Stockholm University, Faculty of Science, Department of Systems Ecology. Stockholm University, Stockholm Resilience Centre.
    Thyresson, Matilda
    Stockholm University, Faculty of Science, Department of Systems Ecology. Stockholm University, Stockholm Resilience Centre.
    Johansson, C.
    The non-linear relationship between body size and function in parrotfihes2008In: Coral reefs (Print), ISSN 0722-4028, E-ISSN 1432-0975, Vol. 27, no 4, p. 967-974Article in journal (Refereed)
    Abstract [en]

    Parrotfishes are a group of herbivores that play an important functional role in structuring benthic communities on coral reefs. Increasingly, these fish are being targeted by fishermen, and resultant declines in biomass and abundance may have severe consequences for the dynamics and regeneration of coral reefs. However, the impact of overfishing extends beyond declining fish stocks. It can also lead to demographic changes within species populations where mean body size is reduced. The effect of reduced mean body size on population dynamics is well described in literature but virtually no information exists on how this may influence important ecological functions. The study investigated how one important function, scraping (i.e., the capacity to remove algae and open up bare substratum for coral larval settlement), by three common species of parrotfishes (Scarus niger, Chlorurus sordidus, and Chlorurus strongylocephalus) on coral reefs at Zanzibar (Tanzania) was influenced by the size of individual fishes. There was a non-linear relationship between body size and scraping function for all species examined, and impact through scraping was also found to increase markedly when fish reached a size of 15-20 cm. Thus, coral reefs which have a high abundance and biomass of parrotfish may nonetheless be functionally impaired if dominated by small-sized individuals. Reductions in mean body size within parrotfish populations could, therefore, have functional impacts on coral reefs that previously have been overlooked.

  • 3. McAndrews, Ryan S.
    et al.
    Eich, Andreas
    Ford, Amanda K.
    Stockholm University, Faculty of Science, Stockholm Resilience Centre. Leibniz Centre for Tropical Marine Research (ZMT), Germany; University of Bremen, Germany.
    Bejarano, Sonia
    Lal, Ronal R.
    Ferse, Sebastian C. A.
    Algae sediment dynamics are mediated by herbivorous fishes on a nearshore coral reef2019In: Coral reefs (Print), ISSN 0722-4028, E-ISSN 1432-0975, Vol. 38, no 3, p. 431-441Article in journal (Refereed)
    Abstract [en]

    Epilithic algae are a ubiquitous component of coral reefs. Components of the epilithic algal matrix (EAM) can have a significant influence on coral settlement and benthic feeding by fishes. We employed a herbivore exclusion experiment on a fringing reef in Viti Levu, Fiji, to investigate the functional role of herbivorous fishes in affecting the EAM between different habitat types and levels of community-based fishing restriction. We surveyed the herbivorous fish community and deployed experimental tiles on the reef flat and lagoonal slope and inside and outside of an area where fishing is restricted (tabu). Tiles were deployed for 3months, half within cages to exclude herbivorous fishes. We then identified algal type and quantified epilithic algal turf height, sediment dry weight, and detritus within the EAM on each tile. EAM that developed under herbivory was remarkably similar, regardless of the differences in habitat or fishing restriction. In contrast, EAM within cages was characterised by longer turf, heavier sediment load, and high variance in turf length and sediment load. Habitat type played a strong role in determining EAM characteristics where herbivores were excluded. Caged EAM on the reef flat was characterised by algal turf and fleshy macroalgae, whereas EAM in cages on the lagoonal slope was overwhelmingly dominated by filamentous and mat-forming cyanobacteria. The results presented here demonstrate the importance of herbivorous fishes in maintaining a benthic environment favourable to coral settlement and survival. Our results suggest that herbivore biomass per se is not a reliable predictor of foraging activity. Moreover, these results show that the absence of herbivore foraging can have different consequences depending on the habitat type, even within the same reef.

  • 4. Mora, Camilo
    et al.
    Graham, Nicholas A. J.
    Nyström, Magnus
    Stockholm University, Faculty of Science, Stockholm Resilience Centre.
    Ecological limitations to the resilience of coral reefs2016In: Coral reefs (Print), ISSN 0722-4028, E-ISSN 1432-0975, Vol. 35, no 4, p. 1271-1280Article, review/survey (Refereed)
    Abstract [en]

    The decline of coral reefs has been broadly attributed to human stressors being too strong and pervasive, whereas biological processes that may render coral reefs fragile have been sparsely considered. Here we review several ecological factors that can limit the ability of coral reefs to withstand disturbance. These include: (1) Many species lack the adaptive capacity to cope with the unprecedented disturbances they currently face; (2) human disturbances impact vulnerable life history stages, reducing reproductive output and the supply of recruits essential for recovery; (3) reefs can be vulnerable to the loss of few species, as niche specialization or temporal and spatial segregation makes each species unique (i.e., narrow ecological redundancy); in addition, many foundation species have similar sensitivity to disturbances, suggesting that entire functions can be lost to single disturbances; and (4) feedback loops and extinction vortices may stabilize degraded states or accelerate collapses even if stressors are removed. This review suggests that the degradation of coral reefs is due to not only the severity of human stressors but also the fragility of coral reefs. As such, appropriate governance is essential to manage stressors while being inclusive of ecological process and human uses across transnational scales. This is a considerable but necessary upgrade in current management if the integrity, and delivery of goods and services, of coral reefs is to be preserved.

  • 5.
    Norstrom, Albert
    et al.
    Stockholm University, Stockholm Resilience Centre.
    Sandstrom, M.
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Lipid content of Favia fragum larvae: changes during planulation2010In: Coral reefs (Print), ISSN 0722-4028, E-ISSN 1432-0975, Vol. 29, no 3, p. 793-795Article in journal (Refereed)
    Abstract [en]

    Lipid content of planula larvae of the brooding scleractinian coral Favia fragum was analysed through a monthly planulation period. The average lipid content per dry weight of F. fragum planulae was 39%, which is low compared with other scleractinian coral species. Lipid content of planulae was significantly affected by the day of release and decreased during the planulation period.

  • 6.
    Nyström, Magnus
    et al.
    Stockholm University, Faculty of Science, Department of Systems Ecology. Stockholm University, Stockholm Resilience Centre.
    Graham, N. A. J.
    Lokrantz, Jerker
    Stockholm University, Faculty of Science, Department of Systems Ecology. Stockholm University, Stockholm Resilience Centre.
    Norström, Albert V.
    Stockholm University, Faculty of Science, Department of Systems Ecology. Stockholm University, Stockholm Resilience Centre.
    Capturing the cornerstones of coral reef resilience: linking theory to practice2008In: Coral reefs (Print), ISSN 0722-4028, E-ISSN 1432-0975, Vol. 27, no 4, p. 795-809Article in journal (Refereed)
    Abstract [en]

    Coral reefs can undergo unexpected and dramatic changes in community composition, so called phase shifts. This can have profound consequences for ecosystem services upon which human welfare depends. Understanding of this behavior is in many aspects still in its infancy. Resilience has been argued to provide insurance against unforeseen ecosystem responses in the face of environmental change, and has become a prime goal for the management of coral reefs. However, diverse definitions of resilience can be found in the literature, making its meaning ambiguous. Several studies have used the term as a theoretical framework and concern regarding its practical applicability has been raised. Consequently, operationalizing theory to make resilience observable is an important task, particularly for policy makers and managers dealing with pressing environmental problems. Ultimately this requires some type of empirical assessments, something that has proven difficult due to the multidimensional nature of the concept. Biodiversity, spatial heterogeneity, and connectivity have been proposed as cornerstones of resilience as they may provide insurance against ecological uncertainty. The aim of this article is to provide an overview of the divergent uses of the concept and to propose empirical indicators of the cornerstones of coral reef resilience. These indicators include functional group approaches, the ratios of "good" and "bad" colonizers of space, measurements of spatial heterogeneity, and estimates of potential space availability against grazing capacity. The essence of these operational indicators of resilience is to use them as predictive tools to recognize vulnerability before disturbance occurs that may lead to abrupt phase shifts. Moving toward operationalizing resilience theory is imperative to the successful management of coral reefs in an increasingly disturbed and human-dominated environment.

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