Intra-Annual Variation in Mesophotic Benthic Assemblages on the Insular Slope of Southwest Puerto Rico as a Function of Depth and Geomorphology

There is limited information on the intra-annual variability of mesophotic coral ecosystems (MCEs), worldwide. The benthic communities, measured as % cover, of two geomorphologically different mesophotic sites (El Hoyo and Hole-in-the-Wall) were examined during 2009–2010 in southwest Puerto Rico. Depths sampled were 50 and 70 m. At each site/depth combination, two permanent transects, measuring 10-m long by 40-cm wide, were surveyed by successive photoquadrants, 0.24 m2 in area. Scleractinian corals, octocorals, macroalgae, crustose coralline algae (CCA), sponges and unconsolidated sediment were the main components along the transects. Significant community differences were observed both among sites and among depths. Differences among sites were greater at 50 m than at 70 m. The El Hoyo site at 50 m was the most divergent, and this was due to a lower coral and sponge cover and a higher algal cover (Amphiroa spp., Peyssonnelia iridescens, turf) relative to the other site/depth combinations. As a consequence, the differences in community structure with depth were larger at El Hoyo than at Hole-in-the-Wall. The communities at 70 m were distinguished from those at 50 m by the greater proportion of the corals Agaricia undata, Madracis pharensis and CCA, and a reduced cover of the cyanobacterium Schizothrix. Temporal variation in the benthic assemblages was documented throughout the year. For both mesophotic sites, the magnitude of change at 50 m was significantly greater than at 70 m. For both depths, the magnitude of change at El Hoyo was significantly greater than at Hole-in-the-Wall. All assemblages experienced almost the same temporal patterns, despite the differences in species composition across sites and depths. Changes in temporal patterns are driven by an increase in the percent cover of the macroalgae Dictyota spp., and a decrease in the percent cover of non-colonized substrata (sand, pavement or rubble). Relatively rapid, intra-annual changes are dictated by the negative correlation between cyclic Dictyota spp. cover and open substrata cover. Other observed mechanisms for rapid community changes in the photoquadrants were diseases and collapses of substrata along with their associated fauna indicating that small-scale disturbance processes may play an important role within MCEs.

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Recent density decline in wild-collected subarctic crustose coralline algae reveals climate change signature

Geology ◽

10.1130/g46804.1 ◽

2019 ◽

Vol 48 (3) ◽

pp. 226-230 ◽

Cited By ~ 3

Author(s):

P.T.W. Chan ◽

J. Halfar ◽

W.H. Adey ◽

P.A. Lebednik ◽

R. Steneck ◽

...

Keyword(s):

Structural Integrity ◽

Benthic Communities ◽

Crustose Coralline Alga ◽

Coralline Algae ◽

Co2 Uptake ◽

Strong Correlations ◽

Crustose Coralline Algae ◽

Skeletal Density ◽

Surface Ocean

Abstract Warming surface ocean temperatures combined with the continued diffusion of atmospheric CO2 into seawater have been shown to have detrimental impacts on calcareous marine organisms in tropical and temperate localities. However, greater oceanic CO2 uptake in higher latitudes may present a higher oceanic acidification risk to carbonate organisms residing in Arctic and subarctic habitats. This is especially true for crustose coralline algae that build their skeletons using high-Mg calcite, which is among the least stable and most soluble of the carbonate minerals. Here we present a century-long annually resolved growth, density, and calcification rate record from the crustose coralline alga Clathromorphum nereostratum, a dominant calcifier in Pacific Arctic and subarctic benthic communities. Specimens were collected from the Aleutian Islands, Alaska (USA), a region that has undergone a long-term decline of 0.08 ± 0.01 pH units since the late 19th century. Growth and calcification rates remain relatively stable throughout the record, but skeletal densities have declined substantially since A.D. 1983. Strong correlations to warming sea-surface temperatures indicate that temperature stress may play a significant role in influencing the ability of corallines to calcify. Decreasing algal skeletal density may offset the benefits of continued growth and calcification due to a weakening in structural integrity, which could have detrimental consequences for the diverse reef-like communities associated with algal structures in mid-to-high latitudes.

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Long-term effects of competition and environmental drivers on the growth of the endangered coral Mussismilia braziliensis (Verril, 1867)

PeerJ ◽

10.7717/peerj.5419 ◽

2018 ◽

Vol 6 ◽

pp. e5419 ◽

Cited By ~ 9

Author(s):

Felipe V. Ribeiro ◽

João A. Sá ◽

Giovana O. Fistarol ◽

Paulo S. Salomon ◽

Renato C. Pereira ◽

...

Keyword(s):

Coral Growth ◽

Coralline Algae ◽

Coral Tissue ◽

Environmental Drivers ◽

Stable Phase ◽

Small Scale ◽

Live Coral ◽

Percent Cover ◽

Study Region ◽

Turbid Zone

Most coral reefs have recently experienced acute changes in benthic community structure, generally involving dominance shifts from slow-growing hard corals to fast-growing benthic invertebrates and fleshy photosynthesizers. Besides overfishing, increased nutrification and sedimentation are important drivers of this process, which is well documented at landscape scales in the Caribbean and in the Indo-Pacific. However, small-scale processes that occur at the level of individual organisms remain poorly explored. In addition, the generality of coral reef decline models still needs to be verified on the vast realm of turbid-zone reefs. Here, we documented the outcome of interactions between an endangered Brazilian-endemic coral (Mussismilia braziliensis) and its most abundant contacting organisms (turf, cyanobacteria, corals, crustose coralline algae and foliose macroalgae). Our study was based on a long (2006–2016) series of high resolution data (fixed photoquadrats) acquired along a cross-shelf gradient that includes coastal unprotected reefs and offshore protected sites. The study region (Abrolhos Bank) comprises the largest and richest coralline complex in the South Atlantic, and a foremost example of a turbid-zone reef system with low diversity and expressive coral cover. Coral growth was significantly different between reefs. Coral-algae contacts predominated inshore, while cyanobacteria and turf contacts dominated offshore. An overall trend in positive coral growth was detected from 2009 onward in the inshore reef, whereas retraction in live coral tissue was observed offshore during this period. Turbidity (+) and cyanobacteria (−) were the best predictors of coral growth. Complimentary incubation experiments, in which treatments of Symbiodinium spp. from M. braziliensis colonies were subjected to cyanobacterial exudates, showed a negative effect of the exudate on the symbionts, demonstrating that cyanobacteria play an important role in coral tissue necrosis. Negative effects of cyanobacteria on living coral tissue may remain undetected from percent cover estimates gathered at larger spatial scales, as these ephemeral organisms tend to be rapidly replaced by longer-living macroalgae, or complex turf-like consortia. The cross-shelf trend of decreasing turbidity and macroalgae abundance suggests either a direct positive effect of turbidity on coral growth, or an indirect effect related to the higher inshore cover of foliose macroalgae, constraining cyanobacterial abundance. It is unclear whether the higher inshore macroalgal abundance (10–20% of reef cover) is a stable phase related to a long-standing high turbidity background, or a contemporary response to anthropogenic stress. Our results challenge the idea that high macroalgal cover is always associated with compromised coral health, as the baselines for turbid zone reefs may derive sharply from those of coral-dominated reefs that dwell under oligotrophic conditions.

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Re-evaluating the health of coral reef communities: baselines and evidence for human impacts across the central Pacific

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2015.1985 ◽

2016 ◽

Vol 283 (1822) ◽

pp. 20151985 ◽

Cited By ~ 110

Author(s):

Jennifer E. Smith ◽

Rusty Brainard ◽

Amanda Carter ◽

Saray Grillo ◽

Clinton Edwards ◽

...

Keyword(s):

Coral Reef ◽

Human Impacts ◽

Phase Shifts ◽

Coralline Algae ◽

Human Populations ◽

Limited Information ◽

Crustose Coralline Algae ◽

Central Pacific ◽

Reef Communities ◽

Coral Reef Communities

Numerous studies have documented declines in the abundance of reef-building corals over the last several decades and in some but not all cases, phase shifts to dominance by macroalgae have occurred. These assessments, however, often ignore the remainder of the benthos and thus provide limited information on the present-day structure and function of coral reef communities. Here, using an unprecedentedly large dataset collected within the last 10 years across 56 islands spanning five archipelagos in the central Pacific, we examine how benthic reef communities differ in the presence and absence of human populations. Using islands as replicates, we examine whether benthic community structure is associated with human habitation within and among archipelagos and across latitude. While there was no evidence for coral to macroalgal phase shifts across our dataset we did find that the majority of reefs on inhabited islands were dominated by fleshy non-reef-building organisms (turf algae, fleshy macroalgae and non-calcifying invertebrates). By contrast, benthic communities from uninhabited islands were more variable but in general supported more calcifiers and active reef builders (stony corals and crustose coralline algae). Our results suggest that cumulative human impacts across the central Pacific may be causing a reduction in the abundance of reef builders resulting in island scale phase shifts to dominance by fleshy organisms.

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Seasonal shifts in the competitive ability of macroalgae influence the outcomes of coral–algal competition

Royal Society Open Science ◽

10.1098/rsos.201797 ◽

2020 ◽

Vol 7 (12) ◽

pp. 201797

Author(s):

Kristen T. Brown ◽

Dorothea Bender-Champ ◽

Ove Hoegh-Guldberg ◽

Sophie Dove

Keyword(s):

Coral Reef ◽

Competitive Ability ◽

Benthic Communities ◽

Coralline Algae ◽

Crustose Coralline Algae ◽

Chemical Mechanisms ◽

Chemical Defences ◽

Natural Processes ◽

Coral Reef Ecosystems ◽

Algal Competition

Understanding the effects of natural processes on coral–algal competition is an important step in identifying the role of macroalgae in perturbed coral reef ecosystems. However, studies investigating coral–algal interactions are often conducted in response to a disturbance, and rarely incorporate seasonal variability. Here, naturally occurring coral–algal interactions were assessed in situ four times a year over 2 years across eight sites spanning diverse benthic communities. In over 6500 recorded coral–algal interactions, cyanobacteria and turf algae were found to be the most damaging regardless of season, resulting in visible damage to coral in greater than 95% of interactions. Macroalgae that primarily compete using chemical mechanisms were found to be more damaging than those that compete using physical mechanisms (e.g. abrasion), with both groups demonstrating decreased competitive ability in summer. While crustose coralline algae were the least damaging to competing coral, during summer, it became three times more competitive. Our results demonstrate that the competitive ability of macroalgae and the outcomes of coral–algal competition can fluctuate in seasonal cycles that may be related to biomass, production of chemical defences and/or physical toughness. The results of this study have important implications for understanding the trajectory and resilience of coral reef ecosystems into the future.

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Comparison between the sponge fauna living outside and inside the coralligenous bioconstruction. A quantitative approach

Mediterranean Marine Science ◽

10.12681/mms.900 ◽

2015 ◽

Vol 16 (2) ◽

pp. 413 ◽

Cited By ~ 17

Author(s):

B. CALCINAI ◽

M. BERTOLINO ◽

G. BAVESTRELLO ◽

S. MONTORI ◽

M. MORI ◽

...

Keyword(s):

Dynamic Equilibrium ◽

Three Dimensional ◽

Taxonomic Diversity ◽

Coralline Algae ◽

Dimensional Structure ◽

Crustose Coralline Algae ◽

Benthic Assemblages ◽

Ligurian Sea ◽

Few Data ◽

Complex Architecture

Coralligenous habitat results from a multi-stratified accumulation of crustose coralline algae and animal builders in a dynamic equilibrium with disruptive agents. The result is a complex architecture crossed by crevices and holes. Due to this three-dimensional structure, coralligenous may host a rich and diversified fauna, more abundant than any other Mediterranean habitat. Unfortunately, very few data are available about the cryptic fauna that lives inside the conglomerate. As already reported for coral reefs, the cryptic fauna plays an important role in the exchange of material and energy between water column and benthic assemblages. Here we compare the sponge community present inside and outside the coralligenous framework of Portofino Promontory (Ligurian Sea) at different depths (15 and 30 meters) not only in terms of taxonomic diversity but for the first time also in term of biomass. Sponges present on the surface of each block were collected, weighed and identified; after blocks dissolution in HCl, target cryptic sponges were separated from other organisms, weighed, and identified. We recorded a total of 62 sponge species. The average number of sponge taxa occurring outside the coralligenous accretions is lower than the number of taxa identified inside. This pattern is confirmed also regarding sponge biomass. These results underlines that studies focused on coralligenous functioning should take in account the important contribution of cryptic fauna, as recently evidenced also for tropical reef habitats.

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The interactive effect of herbivory, nutrient enrichment and mucilage on shallow rocky macroalgal communities

PeerJ ◽

10.7717/peerj.6908 ◽

2019 ◽

Vol 7 ◽

pp. e6908

Author(s):

Sarah Caronni ◽

Chiara Calabretti ◽

Sandra Citterio ◽

Maria Anna Delaria ◽

Rodolfo Gentili ◽

...

Keyword(s):

Mediterranean Sea ◽

Nutrient Enrichment ◽

Marine Protected Area ◽

Interactive Effect ◽

Grazing Pressure ◽

Coralline Algae ◽

Percent Cover ◽

Crustose Coralline Algae ◽

Macroalgal Community ◽

Experimental Treatments

This paper focuses on the interactive short and long-term effect of three different stressors on a macroalgal assemblage. Three stressors are considered: herbivory, nutrients and mucilage. The experiment was conducted in Tavolara Punta Coda Cavallo Marine Protected Area (Mediterranean Sea) during a bloom of the benthic mucilage-producing microalga Chrysophaeum taylorii (Pelagophyceae); this microalga is recently spreading in the Mediterranean Sea. On a rocky substratum, 36 plots 20 × 20 cm in size were prepared. Factorial combinations of three experimental treatments were applied in triplicate, including three grazing levels crossed with two nutrient enrichment and two mucilage removal treatments. Significant differences were observed among treatments 8 weeks later, at the end of summer. In particular, dark filamentous algae were more abundant in all enriched plots, especially where mucilage and macroalgae had been removed; a higher percent cover of crustose coralline algae was instead observed where nutrients had been increased and no grazing pressure acted. Furthermore, the abundance of Dictyota spp. and Laurencia spp. was significantly higher in enriched mucilage-free plots where the grazing pressure was null or low. However, the effects of the treatments on the overall assemblage of the macroalgal community were not long persistent (36 weeks later). These results illustrate the capacity of a shallow-water macroalgal community to quickly recover from the simultaneous impacts of herbivory, nutrient enrichment, and mucilage.

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Tropical crustose coralline algal individual and community responses to elevated pCO2 under high and low irradiance

ICES Journal of Marine Science ◽

10.1093/icesjms/fsv213 ◽

2015 ◽

Vol 73 (3) ◽

pp. 803-813 ◽

Cited By ~ 6

Author(s):

Elizabeth Dutra ◽

Marguerite Koch ◽

Katherine Peach ◽

Carrie Manfrino

Keyword(s):

Benthic Communities ◽

Co2 Enrichment ◽

High Irradiance ◽

Elevated Pco2 ◽

Coralline Algae ◽

Algal Community ◽

Crustose Coralline Algae ◽

Cayman Island ◽

Pco2 Treatment ◽

Diel Cycles

Abstract Crustose coralline algae (CCA) cement reefs and create important habitat and settling sites for reef organisms. The susceptibility of CCA to increasing ocean pCO2 and declining pH or ocean acidification (OA) is a growing concern. Although CCA are autotrophs, there has been little focus on the interaction of elevated pCO2 and irradiance. We examined elevated pCO2 effects on individual CCA and macroalgal benthic communities at high and low irradiance (205–13 µmol photons m−2 s−1) in an aquaria experiment (35 d, June–August 2014) on Little Cayman Island, Caribbean. A dominant Cayman reef wall CCA (Peyssonnelia sp.) in its adult lobed form and individual CCA recruits were used as experimental units. Changes in CCA, fleshy macroalgae (branching and turfs), and microalgae (including microbial biofilm) per cent cover and frequency were examined on macroalgal communities that settled onto plates from the reef. Reef diel cycles of pCO2 and pH were simulated using seawater inflow from a back reef. Although CO2 enrichment to year 2100 levels resulted in 1087 µatm pCO2 in the elevated pCO2 treatment, CaCO3 saturation states remained high (Ωcal ≥ 2.7). Under these conditions, elevated pCO2 had no effect on Peyssonnelia sp. calcification rates or survival regardless of irradiance. Individual CCA surface area on the bottom of settling plates was lower under elevated pCO2, but per cent cover or frequency within the community was unchanged. In contrast, there was a strong and consistent community assemblage response to irradiance. Microalgae increased at high irradiance and CCA increased under low irradiance with no significant pCO2 interaction. Based on this short-term experiment, tropical macroalgal communities are unlikely to shift at pCO2 levels predicted for year 2100 under high or low irradiance. Rather, irradiance and other factors that promote microalgae are likely to be strong drivers of tropical benthic algal community structure under climate change.

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Sedimentation and overfishing drive changes in early succession and coral recruitment

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2020.2575 ◽

2020 ◽

Vol 287 (1941) ◽

pp. 20202575

Author(s):

Ama Wakwella ◽

Peter J. Mumby ◽

George Roff

Keyword(s):

Environmental Gradients ◽

Management Strategies ◽

Sediment Accumulation ◽

Three Dimensional ◽

Coralline Algae ◽

Strong Interactions ◽

Crustose Coralline Algae ◽

Coral Recruitment ◽

Benthic Assemblages ◽

Cascading Effects

Sedimentation and overfishing are important local stressors on coral reefs that can independently result in declines in coral recruitment and shifts to algal-dominated states. However, the role of herbivory in driving recovery across environmental gradients is often unclear. Here we investigate early successional benthic communities and coral recruitment across a sediment gradient in Palau, Micronesia over a 12-month period. Total sedimentation rates measured by ‘TurfPods’ varied from 0.03 ± 0.1 SE mg cm −2 d −1 at offshore sites to 1.32 ± 0.2 mg cm −2 d −1 at inshore sites. To assess benthic succession, three-dimensional settlement tiles were deployed at sites with experimental cages used to exclude tile access to larger herbivorous fish. Benthic assemblages exhibited rapid transitions across the sediment gradient within three months of deployment. At low levels of sedimentation (less than 0.6 mg cm −2 d −1 ), herbivory resulted in communities dominated by coral recruitment inducers (short turf algae and crustose coralline algae), whereas exclusion of herbivores resulted in the overgrowth of coral inhibitors (encrusting and upright foliose macroalgae). An ‘inducer threshold’ was found under increasing levels of sedimentation (greater than 0.6 mg cm −2 d −1 ), with coral inducers having limited to no presence in communities, and herbivore access to tiles resulted in sediment-laden turf algal assemblages, while exclusion of herbivores resulted in invertebrates (sponges, ascidians) and terrestrial sediment accumulation. A ‘coral recruitment threshold’ was found at 0.8 mg cm −2 d −1 , below which net coral recruitment was reduced by 50% in the absence of herbivores, while recruitment was minimal above the threshold. Our results highlight nonlinear trajectories of benthic succession across sediment gradients and identify strong interactions between sediment and herbivory that have cascading effects on coral recruitment. Local management strategies that aim to reduce sedimentation and turbidity and manage herbivore fisheries can have measurable effects on benthic community succession and coral recruitment, enhancing reef resilience and driving coral recovery.

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The collapse of marine forests: drastic reduction in populations of the family Sargassaceae in Madeira Island (NE Atlantic)

Regional Environmental Change ◽

10.1007/s10113-021-01801-2 ◽

2021 ◽

Vol 21 (3) ◽

Author(s):

Alejandro Bernal-Ibáñez ◽

Ignacio Gestoso ◽

Peter Wirtz ◽

Manfred Kaufmann ◽

Ester A. Serrão ◽

...

Keyword(s):

Sea Urchins ◽

Anthropogenic Impacts ◽

Benthic Communities ◽

Coralline Algae ◽

North Coast ◽

Anthropogenic Pressure ◽

Historical Records ◽

Crustose Coralline Algae ◽

Ne Atlantic ◽

Madeira Island

AbstractSpecies of the genera Cystoseira, Ericaria, Gongolaria, and Sargassum (family Sargassaceae) are key components of the Mediterranean-Atlantic marine forests, essential for biodiversity and ecosystem functioning. Populations of these foundational species are particularly vulnerable to anthropogenic impacts, likely to be intensified under future scenarios of climate change. The decline and even disappearance of these species have been reported in different areas of the world. At Madeira Island (NE Atlantic), populations of Gongolaria abies-marina, Ericaria selaginoides, Sargassum vulgare, and Sargassum filipendula, the most ecologically relevant species in Macaronesian marine forests, have been suffering a drastic decline during the last decades, especially on the southern coast of the island, where anthropogenic pressure is higher than on the north coast. The lack of sufficient temporal coverage on qualitative and quantitative studies of Sargassaceae communities in Madeira poses a challenge to establish a specific period for this decline. Consulting qualitative studies and historical records, we have set for the first time a timeline that shows an evident decrease in Sargassaceae populations in the last 20 years on Madeira Island. Following this timeline, we pinpoint the start of this decline in the first decade of the 2000s. This can be particularly confirmed for places like Funchal and Reis Magos, with significantly higher historical records. Currently, most benthic communities on shallow subtidal rocky reefs along the south coast are dominated by sea urchins and crustose coralline algae, the so-called sea urchin barrens. However, in some cases, they are entirely covered by a layer of sediment. We discuss the possible factors contributing to these drastic changes, bringing Madeira’s marine forests to a dramatic decline. As many animal species rely on marine forests, the decline of Sargassaceae populations represents an invaluable ecological loss for the coastal ecosystem of the island.

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Bioerosion of reef-building crustose coralline algae by endolithic invertebrates in an upwelling-influenced reef

Coral Reefs ◽

10.1007/s00338-021-02065-2 ◽

2021 ◽

Author(s):

Alexandra Ramírez-Viaña ◽

Guillermo Diaz-Pulido ◽

Rocío García-Urueña

Keyword(s):

Coralline Algae ◽

Crustose Coralline Algae

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