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

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.

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

Geology ◽  
2019 ◽  
Vol 48 (3) ◽  
pp. 226-230 ◽  
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.

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

2021 ◽  
Vol 8 ◽  
Author(s):  
Richard S. Appeldoorn ◽  
David L. Ballantine ◽  
Milton Carlo ◽  
Juan J. Cruz Motta ◽  
Michael Nemeth ◽  
...  
Keyword(s):  
Puerto Rico ◽  
Benthic Communities ◽  
Temporal Patterns ◽  
Coralline Algae ◽  
Small Scale ◽  
Percent Cover ◽  
Limited Information ◽  
Crustose Coralline Algae ◽  
Benthic Assemblages ◽  
Disturbance Processes

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.

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

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.

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

PeerJ ◽  
2021 ◽  
Vol 9 ◽  
pp. e10696
Author(s):  
Xochitl E. Elías Ilosvay ◽  
Johanna Segovia ◽  
Sebastian Ferse ◽  
Walter Ernesto Elias ◽  
Christian Wild
Keyword(s):  
El Salvador ◽  
Benthic Community ◽  
Anthropogenic Impacts ◽  
Coral Cover ◽  
Benthic Algae ◽  
Coralline Algae ◽  
Crustose Coralline Algae ◽  
Night Time ◽  
Herbivore Exclusion ◽  
Turf Algae

The Eastern Tropical Pacific (ETP) is one of the most isolated and least studied regions in the world. This particularly applies to the coast of El Salvador, where the only reef between Guatemala and Nicaragua, called Los Cóbanos reef, is located. There is very little published information about the reef’s biodiversity, and to our knowledge, no research on its ecology and responses to anthropogenic impacts, such as overfishing, has been conducted. The present study, therefore, described the benthic community of Los Cóbanos reef, El Salvador, using the Line-Point-Intercept-Transect method and investigated changes in the benthic community following the exclusion of piscine macroherbivores over a period of seven weeks. Results showed high benthic algae cover (up to 98%), dominated by turf and green algae, and low coral cover (0–4%). Porites lobata was the only hermatypic coral species found during the surveys. Surprisingly, crustose coralline algae (CCA) showed a remarkable total cover increase by 58%, while turf algae cover decreased by 82%, in experimental plots after seven weeks of piscine macroherbivore exclusion. These findings apparently contradict the results of most previous similar studies. While it was not possible to ascertain the exact mechanisms leading to these drastic community changes, the most likely explanation is grazing on turf by small grazing macroherbivores that had access to the cages during the experiment and clearing of CCA initially covered by epiphytes and sediments. A higher CCA cover would promote the succesful settlement by corals and prevent further erosion of the reef framework. Therefore it is crucial to better understand algal dynamics, herbivory, and implications of overfishing at Los Cóbanos to avoid further reef deterioration. This could be achieved through video surveys of the fish community, night-time observations of the macroinvertebrate community, exclusion experiments that also keep out herbivorous macroinvertebrates, and/or experimental assessments of turf algae/CCA interactions.

scholarly journals 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 ◽  
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.

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

2015 ◽  
Vol 73 (3) ◽  
pp. 803-813 ◽  
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.

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

Coral Reefs ◽  
2021 ◽  
Author(s):  
Alexandra Ramírez-Viaña ◽  
Guillermo Diaz-Pulido ◽  
Rocío García-Urueña
Keyword(s):  
Coralline Algae ◽  
Crustose Coralline Algae

Synergistic effects of diuron and sedimentation on photosynthesis and survival of crustose coralline algae

2005 ◽  
Vol 51 (1-4) ◽  
pp. 415-427 ◽  
Author(s):  
Lindsay Harrington ◽  
Katharina Fabricius ◽  
Geoff Eaglesham ◽  
Andrew Negri
Keyword(s):  
Synergistic Effects ◽  
Coralline Algae ◽  
Crustose Coralline Algae

Effect of 3D printer enabled surface morphology and composition on coral growth in artificial reefs

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Ilse Valenzuela Matus ◽  
Jorge Lino Alves ◽  
Joaquim Góis ◽  
Augusto Barata da Rocha ◽  
Rui Neto ◽  
...  
Keyword(s):  
Additive Manufacturing ◽  
Chemical Composition ◽  
Chemical Elements ◽  
Three Dimensional ◽  
Coral Growth ◽  
Coralline Algae ◽  
Textured Surface ◽  
Crustose Coralline Algae ◽  
Statistical Parameters ◽  
Content Type

Purpose The purpose of this paper is to prove and qualify the influence of textured surface substrates morphology and chemical composition on the growth and propagation of transplanted corals. Use additive manufacturing and silicone moulds for converting three-dimensional samples into limestone mortar with white Portland cement substrates for coral growth. Design/methodology/approach Tiles samples were designed and printed with different geometries and textures inspired by nature marine environment. Commercial coral frag tiles were analysed through scanning electron microscopy (SEM) to identify the main chemical elements. Raw materials and coral species were selected. New base substrates were manufactured and deployed into a closed-circuit aquarium to monitor the coral weekly evolution process and analyse the results obtained. Findings Experimental results provided positive statistical parameters for future implementation tests, concluding that the intensity of textured surface, interfered favourably in the coralline algae biofilm growth. The chemical composition and design of the substrates were determinant factors for successful coral propagation. Recesses and cavities mimic the natural rocks aspect and promoted the presence and interaction of other species that favour the richness of the ecosystem. Originality/value Additive manufacturing provided an innovative method of production for ecology restoration areas, allowing rapid prototyping of substrates with high complexity morphologies, a critical and fundamental attribute to guarantee coral growth and Crustose Coralline Algae. The result of this study showed the feasibility of this approach using three-dimensional printing technologies.

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