Rapid relative increase of crustose coralline algae following herbivore exclusion in a reef of El Salvador

Competition between reef-building corals and benthic algae is of key importance for reef dynamics. These interactions occur on many spatial scales, ranging from chemical to regional. Using microprobes, 16S rDNA pyrosequencing and underwater surveys, we examined the interactions between the reef-building coral Montastraea annularis and four types of benthic algae. The macroalgae Dictyota bartayresiana and Halimeda opuntia , as well as a mixed consortium of turf algae, caused hypoxia on the adjacent coral tissue. Turf algae were also associated with major shifts in the bacterial communities at the interaction zones, including more pathogens and virulence genes. In contrast to turf algae, interactions with crustose coralline algae (CCA) and M. annularis did not appear to be antagonistic at any scale. These zones were not hypoxic, the microbes were not pathogen-like and the abundance of coral–CCA interactions was positively correlated with per cent coral cover. We propose a model in which fleshy algae (i.e. some species of turf and fleshy macroalgae) alter benthic competition dynamics by stimulating bacterial respiration and promoting invasion of virulent bacteria on corals. This gives fleshy algae a competitive advantage over corals when human activities, such as overfishing and eutrophication, remove controls on algal abundance. Together, these results demonstrate the intricate connections and mechanisms that structure coral reefs.

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Slow Community Development Enhances Abiotic Limitation of Benthic Community Structure in a High Arctic Kelp Bed

Frontiers in Marine Science ◽

10.3389/fmars.2021.592295 ◽

2021 ◽

Vol 8 ◽

Author(s):

Christina Bonsell ◽

Kenneth H. Dunton

Keyword(s):

Community Structure ◽

Community Development ◽

Benthic Community ◽

Beaufort Sea ◽

High Arctic ◽

Coralline Algae ◽

Physical Factors ◽

Crustose Coralline Algae ◽

Benthic Community Structure ◽

Kelp Bed

We examined the patterns of propagule recruitment to assess the timescale and trajectory of succession and the possible roles of physical factors in controlling benthic community structure in a shallow High Arctic kelp bed in the Beaufort Sea, Alaska. Spatial differences in established epilithic assemblages were evaluated against static habitat attributes (depth, distance from river inputs) and environmental factors (temperature, salinity, current speed, underwater light) collected continuously over 2–6 years. Our measurements revealed that bottom waters remained below freezing (mean winter temperatures ∼−1.8°C) and saline (33–36) with negligible light levels for 8–9 months. In contrast, the summer open water period was characterized by variable salinities (22–36), higher temperatures (up to 8–9°C) and measurable irradiance (1–8 mol photons m–2 day–1). An inshore, near-river site experienced strong, acute, springtime drops in salinity to nearly 0 in some years. The epilithic community was dominated by foliose red algae (47–79%), prostrate kelps (2–19%), and crustose coralline algae (0–19%). Strong spatial distinctions among sites included a positive correlation between cover by crustose coralline algae and distance to river inputs, but we found no significant relationships between multi-year means of physical factors and functional groups. Low rates of colonization and the very slow growth rates of recruits are the main factors that contribute to prolonged community development, which augments the influence of low-frequency physical events over local community structure. Mortality during early succession largely determines crustose coralline algal and invertebrate prevalence in the established community, while kelp seem to be recruitment-limited. On scales > 1 m, community structure varies with bathymetry and exposure to freshwater intrusion, which regulate frequency of primary and physiological disturbance. Colonization rates (means of 3.3–69.9 ind. 100 cm–1 year–1 site–1) were much lower than studies in other Arctic kelp habitats, and likely reflect the nature of a truly High Arctic environment. Our results suggest that community development in the nearshore Beaufort Sea occurs over decades, and is affected by combinations of recruitment limitation, primary disturbance, and abiotic stressors. While seasonality exerts strong influence on Arctic systems, static habitat characteristics largely determine benthic ecosystem structure by integrating seasonal and interannual variability over timescales longer than most ecological studies.

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Associations between Benthic Cover and Habitat Complexity Metrics Obtained from 3D Reconstruction of Coral Reefs at Different Resolutions

Remote Sensing ◽

10.3390/rs12061011 ◽

2020 ◽

Vol 12 (6) ◽

pp. 1011 ◽

Cited By ~ 2

Author(s):

Atsuko Fukunaga ◽

John H. R. Burns ◽

Kailey H. Pascoe ◽

Randall K. Kosaki

Keyword(s):

Fractal Dimension ◽

Coral Reefs ◽

Habitat Structure ◽

Coral Cover ◽

Three Dimensional ◽

Structural Complexity ◽

Coralline Algae ◽

Crustose Coralline Algae ◽

Surface Areas ◽

Abundance And Diversity

Quantifying the three-dimensional (3D) habitat structure of coral reefs is an important aspect of coral reef monitoring, as habitat architecture affects the abundance and diversity of reef organisms. Here, we used photogrammetric techniques to generate 3D reconstructions of coral reefs and examined relationships between benthic cover and various habitat metrics obtained at six different resolutions of raster cells, ranging from 1 to 32 cm. For metrics of 3D structural complexity, fractal dimension, which utilizes information on 3D surface areas obtained at different resolutions, and vector ruggedness measure (VRM) obtained at 1-, 2- or 4-cm resolution correlated well with benthic cover, with a relatively large amount of variability in these metrics being explained by the proportions of corals and crustose coralline algae. Curvature measures were, on the other hand, correlated with branching and mounding coral cover when obtained at 1-cm resolution, but the amount of variability explained by benthic cover was generally very low when obtained at all other resolutions. These results show that either fractal dimension or VRM obtained at 1-, 2- or 4-cm resolution, along with curvature obtained at 1-cm resolution, can effectively capture the 3D habitat structure provided by specific benthic organisms.

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Factors Affecting Coral Recruitment and Calcium Carbonate Accretion Rates on a Central Pacific Coral Reef

10.26686/wgtn.17057996 ◽

2021 ◽

Author(s):

◽

Franziska Elmer

Keyword(s):

Coral Reef ◽

Calcium Carbonate ◽

Coral Reefs ◽

Benthic Community ◽

Coral Cover ◽

Coralline Algae ◽

Benthic Organisms ◽

Coral Recruitment ◽

Central Pacific ◽

Accretion Rates

<p>Coral recruitment and calcium carbonate (CaCO₃) accretion are fundamental processes that help maintain coral reefs. Many reefs worldwide have experienced degradation, including a decrease in coral cover and biodiversity. Successful coral recruitment helps degraded reefs to recover, while CaCO₃ accretion by early successional benthic organisms maintains the topographic complexity of a coral reef system. It is therefore important to understand the processes that affect coral recruitment and CaCO₃ accretion rates in order to understand how coral reefs recover from disturbances. The aim of this thesis was to determine how biophysical forcing factors affect coral recruitment, calcification and bioerosion on a pristine coral reef. I used artificial settlement tiles to measure coral recruitment and CaCO₃ accretion at ten sites (four on the fore reef, four on the Western Reef Terrace and two at the Entrance Channel) at Palmyra Atoll. Fungia skeletons and pieces of dead coral rock were used to measure bioerosion rates, which were combined with the CaCO₃ accretion rates to obtain a net CaCO₃ budget of the reef substratum. Interactions between coral recruits and other benthic organisms on the settlement tiles were recorded to determine the settlement preferences and competitive strength of coral recruits. The settlement preference of Pocillopora damicornis for divots shaped like steephead and bumphead parrotfish bites marks was determined by adding P. damicornis larvae to a container with a settlement tile with the aforementioned divots. I found that coral recruitment and CaCO₃ accretion are influenced by biophysical forcing factors. Most pocilloporids likely recruit close to their parents while the origin of poritid larvae is much more distant. Pocilloporid recruitment rates were also significantly correlated with the successional stage of the benthic community on the settlement tiles, especially the cover of biofilm and bryozoa. Biofilm and crustose coralline algae (CCA) were preferred as settlement substrata by coral larvae, however both pocilloporids and poritids settled on a large number of different benthic substrata. P. damicornis larvae showed a significant settlement preference for divots shaped like parrotfish bite marks over a flat settlement surface. Coral recruits were good competitors against encrusting algae but were often outcompeted by filamentous and upright algae. Settlement tiles were almost entirely colonised by benthic organisms within three to twelve months of deployment. The mass of CaCO₃ deposited onto the settlement tiles negatively correlated with herbivore grazing pressure on the benthic community. Bioerosion rates within pieces of coral (internal bioerosion) increased over time but overall bioerosion rates (internal and external) rarely exceeded CaCO₃ deposition by CCA. My results show how variability in biophysical forcing factors leads to natural variation in coral recruitment and CaCO₃ accretion. This thesis highlights the importance of measuring herbivore grazing, CCA and turf algae cover to gain a better understanding of reef resilience. I conclude that models constructed for Caribbean reefs may not be suited to predict resilience in Pacific reefs and that within the Pacific, two different kinds of resilience models need to be constructed, one for human-inhabited coral reefs and one for uninhabited coral reefs.</p>

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Indicators of coral reef ecosystem recovery following reduction in logging and implementation of community-based management schemes in the Solomon Islands.

Pacific Conservation Biology ◽

10.1071/pc140075 ◽

2014 ◽

Vol 20 (1) ◽

pp. 75 ◽

Cited By ~ 5

Author(s):

S Albert ◽

A Grinham ◽

B Gibbes ◽

I Tibbetts ◽

J udy

Keyword(s):

Water Quality ◽

Management Practices ◽

Pacific Islands ◽

Coral Cover ◽

Solomon Islands ◽

Coralline Algae ◽

Herbivorous Fish ◽

Crustose Coralline Algae ◽

Ecosystem Recovery ◽

Community Based

The livelihood of many coastal communities in the Pacific Islands is directly dependent on the health of adjacent coral reefs. Reduction in water quality and over-harvesting of herbivorous fish are known to drive reef ecosystems towards a more degraded state. Community-based resource management practices have the potential to improve damaged reefs but quantitative data on their effectiveness remains largely unreported. This study investigated how land use changes and implementation of marine management influenced water quality, herbivorous fish biomass and reef condition of Marovo Lagoon in the Solomon Islands. Four study sites were located along a gradient of water quality, with two of the sites located inside marine protected areas (MPAs) designated in 2006. The results suggest that water quality in coastal areas adjacent to catchments modified by logging was negatively impacted. However, following natural revegetation of bare soil in the catchment between 2000 and 2010, water quality improved at all sites. The biomass of herbivorous fish was significantly greater in the MPAs compared to other sites and, importantly, we detected an increase in herbivore biomass between 2005 and 2008. Inshore reefs adjacent to logging operations had significantly lower coral cover and higher macroalgal cover than those offshore. Between 2005 and 2008 all sites showed an increase in crustose coralline algae cover and a decrease in turf algae colonising rocks, with the changes indicative of improving reef health. Collectively, these results indicate that reduction in logging and implementation of community-based management can have a positive influence on reefs in Marovo Lagoon.

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Factors Affecting Coral Recruitment and Calcium Carbonate Accretion Rates on a Central Pacific Coral Reef

10.26686/wgtn.17057996.v1 ◽

2021 ◽

Author(s):

◽

Franziska Elmer

Keyword(s):

Coral Reef ◽

Calcium Carbonate ◽

Coral Reefs ◽

Benthic Community ◽

Coral Cover ◽

Coralline Algae ◽

Benthic Organisms ◽

Coral Recruitment ◽

Central Pacific ◽

Accretion Rates

<p>Coral recruitment and calcium carbonate (CaCO₃) accretion are fundamental processes that help maintain coral reefs. Many reefs worldwide have experienced degradation, including a decrease in coral cover and biodiversity. Successful coral recruitment helps degraded reefs to recover, while CaCO₃ accretion by early successional benthic organisms maintains the topographic complexity of a coral reef system. It is therefore important to understand the processes that affect coral recruitment and CaCO₃ accretion rates in order to understand how coral reefs recover from disturbances. The aim of this thesis was to determine how biophysical forcing factors affect coral recruitment, calcification and bioerosion on a pristine coral reef. I used artificial settlement tiles to measure coral recruitment and CaCO₃ accretion at ten sites (four on the fore reef, four on the Western Reef Terrace and two at the Entrance Channel) at Palmyra Atoll. Fungia skeletons and pieces of dead coral rock were used to measure bioerosion rates, which were combined with the CaCO₃ accretion rates to obtain a net CaCO₃ budget of the reef substratum. Interactions between coral recruits and other benthic organisms on the settlement tiles were recorded to determine the settlement preferences and competitive strength of coral recruits. The settlement preference of Pocillopora damicornis for divots shaped like steephead and bumphead parrotfish bites marks was determined by adding P. damicornis larvae to a container with a settlement tile with the aforementioned divots. I found that coral recruitment and CaCO₃ accretion are influenced by biophysical forcing factors. Most pocilloporids likely recruit close to their parents while the origin of poritid larvae is much more distant. Pocilloporid recruitment rates were also significantly correlated with the successional stage of the benthic community on the settlement tiles, especially the cover of biofilm and bryozoa. Biofilm and crustose coralline algae (CCA) were preferred as settlement substrata by coral larvae, however both pocilloporids and poritids settled on a large number of different benthic substrata. P. damicornis larvae showed a significant settlement preference for divots shaped like parrotfish bite marks over a flat settlement surface. Coral recruits were good competitors against encrusting algae but were often outcompeted by filamentous and upright algae. Settlement tiles were almost entirely colonised by benthic organisms within three to twelve months of deployment. The mass of CaCO₃ deposited onto the settlement tiles negatively correlated with herbivore grazing pressure on the benthic community. Bioerosion rates within pieces of coral (internal bioerosion) increased over time but overall bioerosion rates (internal and external) rarely exceeded CaCO₃ deposition by CCA. My results show how variability in biophysical forcing factors leads to natural variation in coral recruitment and CaCO₃ accretion. This thesis highlights the importance of measuring herbivore grazing, CCA and turf algae cover to gain a better understanding of reef resilience. I conclude that models constructed for Caribbean reefs may not be suited to predict resilience in Pacific reefs and that within the Pacific, two different kinds of resilience models need to be constructed, one for human-inhabited coral reefs and one for uninhabited coral reefs.</p>

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Dynamics in benthic community composition and influencing factors in an upwelling-exposed coral reef on the Pacific coast of Costa Rica

PeerJ ◽

10.7717/peerj.1434 ◽

2015 ◽

Vol 3 ◽

pp. e1434 ◽

Cited By ~ 7

Author(s):

Ines Stuhldreier ◽

Celeste Sánchez-Noguera ◽

Florian Roth ◽

Carlos Jiménez ◽

Tim Rixen ◽

...

Keyword(s):

Coral Reef ◽

Costa Rica ◽

Influencing Factors ◽

Community Composition ◽

Benthic Community ◽

Pacific Coast ◽

Environmental Changes ◽

Coralline Algae ◽

Nutrient Concentrations ◽

Turf Algae

Seasonal upwelling at the northern Pacific coast of Costa Rica offers the opportunity to investigate the effects of pronounced changes in key water parameters on fine-scale dynamics of local coral reef communities. This study monitored benthic community composition at Matapalo reef (10.539°N, 85.766°W) by weekly observations of permanent benthic quadrats from April 2013 to April 2014. Monitoring was accompanied by surveys of herbivore abundance and biomass and measurements of water temperature and inorganic nutrient concentrations. Findings revealed that the reef-building coralsPocilloporaspp. exhibited an exceptional rapid increase from 22 to 51% relative benthic cover. By contrast, turf algae cover decreased from 63 to 24%, resulting in a corresponding increase in crustose coralline algae cover. The macroalgaCaulerpa sertularioidescovered up to 15% of the reef in April 2013, disappeared after synchronized gamete release in May, and subsequently exhibited slow regrowth. Parallel monitoring of influencing factors suggest thatC. sertularioidescover was mainly regulated by their reproductive cycle, while that of turf algae was likely controlled by high abundances of herbivores. Upwelling events in February and March 2014 decreased mean daily seawater temperatures by up to 7 °C and increased nutrient concentrations up to 5- (phosphate) and 16-fold (nitrate) compared to mean values during the rest of the year. Changes in benthic community composition did not appear to correspond to the strong environmental changes, but rather shifted from turf algae to hard coral dominance over the entire year of observation. The exceptional high dynamic over the annual observation period encourages further research on the adaptation potential of coral reefs to environmental variability.

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Implications of 2D versus 3D surveys to measure the abundance and composition of benthic coral reef communities

Coral Reefs ◽

10.1007/s00338-021-02118-6 ◽

2021 ◽

Author(s):

Niklas A. Kornder ◽

Jose Cappelletto ◽

Benjamin Mueller ◽

Margaretha J. L. Zalm ◽

Stephanie J. Martinez ◽

...

Keyword(s):

Coral Reef ◽

Benthic Community ◽

Trophic Ecology ◽

Coral Cover ◽

3D Structure ◽

Coralline Algae ◽

Surface Cover ◽

Reef Communities ◽

Encrusting Sponges ◽

Coral Reef Communities

AbstractA paramount challenge in coral reef ecology is to estimate the abundance and composition of the communities residing in such complex ecosystems. Traditional 2D projected surface cover estimates neglect the 3D structure of reefs and reef organisms, overlook communities residing in cryptic reef habitats (e.g., overhangs, cavities), and thus may fail to represent biomass estimates needed to assess trophic ecology and reef function. Here, we surveyed the 3D surface cover, biovolume, and biomass (i.e., ash-free dry weight) of all major benthic taxa on 12 coral reef stations on the island of Curaçao (Southern Caribbean) using structure-from-motion photogrammetry, coral point counts, in situ measurements, and elemental analysis. We then compared our 3D benthic community estimates to corresponding estimates of traditional 2D projected surface cover to explore the differences in benthic community composition using different metrics. Overall, 2D cover was dominated (52 ± 2%, mean ± SE) by non-calcifying phototrophs (macroalgae, turf algae, benthic cyanobacterial mats), but their contribution to total reef biomass was minor (3.2 ± 0.6%). In contrast, coral cover (32 ± 2%) more closely resembled coral biomass (27 ± 6%). The relative contribution of erect organisms, such as gorgonians and massive sponges, to 2D cover was twofold and 11-fold lower, respectively, than their contribution to reef biomass. Cryptic surface area (3.3 ± 0.2 m2 m−2planar reef) comprised half of the total reef substrate, rendering two thirds of coralline algae and almost all encrusting sponges (99.8%) undetected in traditional assessments. Yet, encrusting sponges dominated reef biomass (35 ± 18%). Based on our quantification of exposed and cryptic reef communities using different metrics, we suggest adjustments to current monitoring approaches and highlight ramifications for evaluating the ecological contributions of different taxa to overall reef function. To this end, our metric conversions can complement other benthic assessments to generate non-invasive estimates of the biovolume, biomass, and elemental composition (i.e., standing stocks of organic carbon and nitrogen) of Caribbean coral reef communities.

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Assessing Fine-Scale Distribution and Volume of Mediterranean Algal Reefs through Terrain Analysis of Multibeam Bathymetric Data. A Case Study in the Southern Adriatic Continental Shelf

Water ◽

10.3390/w12010157 ◽

2020 ◽

Vol 12 (1) ◽

pp. 157

Author(s):

Fabio Marchese ◽

Valentina Alice Bracchi ◽

Giulia Lisi ◽

Daniela Basso ◽

Cesare Corselli ◽

...

Keyword(s):

Continental Shelf ◽

Ad Hoc ◽

Anthropogenic Impacts ◽

Structural Complexity ◽

Coralline Algae ◽

Global Changes ◽

Terrain Analysis ◽

Crustose Coralline Algae ◽

Bathymetric Data ◽

The Mediterranean

In the Mediterranean Sea, crustose coralline algae form endemic algal reefs known as Coralligenous (C) build-ups. The high degree of complexity that C can reach through time creates notable environmental heterogeneity making C a major hotspot of biodiversity for the Mediterranean basin. C build-up can variably modify the submarine environment by affecting the evolution of submerged landforms, although its role is still far from being systematically defined. Our work proposes a new, ad-hoc semi-automated, GIS-based methodology to map the distribution of C build-ups in shallow coastal waters using high-resolution bathymetric data, collected on a sector of the southern Apulian continental shelf (Southern Adriatic Sea, Italy). Our results quantitatively define the 3D distribution of C in terms of area and volume, estimating more than 103,000 build-ups, covering an area of roughly 305,200 m2, for a total volume of 315,700 m3. Our work firstly combines acoustic survey techniques and geomorphometric analysis to develop innovative approaches for eco-geomorphological studies. The obtained results can contribute to a better definition of the ocean carbon budget, and to the monitoring of local anthropogenic impacts (e.g., bottom trawling damage) and global changes, like ocean warming and acidification. These can affect the structural complexity and total volume of carbonate deposits characterizing the Mediterranean benthic environment.

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A cross-ocean comparison of responses to settlement cues in reef-building corals

10.7287/peerj.preprints.264v1 ◽

2014 ◽

Author(s):

Sarah W Davies ◽

Eli Meyer ◽

Sarah M Guermond ◽

Mikhail V Matz

Keyword(s):

Climate Change ◽

Coral Species ◽

Coral Cover ◽

Coralline Algae ◽

Crustose Coralline Algae ◽

Coral Recruitment ◽

Coral Larvae ◽

Settlement Cues ◽

The Pacific ◽

Caribbean Coral

Caribbean coral reefs have deteriorated substantially over the past 30 years, which is broadly attributable to the effects of global climate change. In the same time, Indo-Pacific reefs maintain higher coral cover and typically recover rapidly after disturbances. This difference in reef resilience is largely due to much higher coral recruitment rates in the Pacific. We hypothesized that the lack of Caribbean coral recruitment might be explained by diminishing quality of settlement cues and/or impaired sensitivity of Caribbean coral larvae to those cues, relative to the Pacific. To evaluate this hypothesis, we assembled a collection of bulk samples of reef encrusting communities, mostly consisting of crustose coralline algae (CCA), from various reefs around the world and tested them as settlement cues for several coral species originating from different ocean provinces. Cue samples were meta-barcoded to evaluate their taxonomic diversity. We observed no systematic differences either in cue potency or in strength of larval responses depending on the ocean province, and no preference of coral larvae towards cues from the same ocean. Instead, we detected significant differences in cue preferences among coral species, even for corals originating from the same reef. We conclude that the region-wide disruption of the settlement process is unlikely to be the major cause of Caribbean reef loss. However, due to their high sensitivity to the effects of climate change, shifts in the composition of CCA-associated communities, combined with pronounced differences in cue preferences among coral species, could substantially influence future coral community structure.

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