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Relationship between macroalgal and coral cover on the reefs included in the study. Data are from the first (A) and last (B) survey of each reef only. The relationship between macroalgal and coral cover is virtually identical. Note the absence of two distinct clusters of reefs, one with high coral and low macroalgal cover and the other with low coral and high macroalgal cover, which would have been predicted by the hypothesis of alternative stable states.
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Caribbean reefs have experienced unprecedented changes in the past four decades. Of great concern is the perceived widespread shift from coral to macroalgal dominance and the question of whether it represents a new, stable equilibrium for coral-reef communities. The primary causes of the shift—grazing pressure (top-down), nutrient loading (bottom-u...
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The 1983-1984 die-off of the long-spined sea urchin Diadema antillarum stands out as a catastrophic marine event because of its detrimental effects on Caribbean coral reefs. Without the grazing activities of this key herbivore, turf and macroalgae became the dominant benthic group, inhibiting coral recruitment and compromising coral reef recovery f...
Changes in the environment disrupt the balance of coral reef ecosystems and able to change the structure of communities from coral reefs to macroalgae communities. This study analyzed the growth of alga turf in Acropora branched corals. Experiments carried out in nature, specifically in the waters around Barranglompo Island, with a growth monitorin...
In the past decades, one of the most widely reported phenomena on Caribbean reefs is the general fall in coral cover and rise in macroalgae. Reefs with low coral cover and high macroalgal abun-dances are often presumed to provide poorer ecosystem functions and services. In this study, we assessed the condition of coral reefs on the Caribbean Coast...
Marine vegetated habitats such as seagrass, mangroves, and macroalgae are common along tropical coastlines globally and provide habitats for a diversity of fishes, including juvenile fish and species found on coral reefs. Understanding the use of these habitats by different fish species and life stages is fundamental to spatial planning, fisheries...
Theory and empirical work suggest that coral reefs may exhibit alternative stable states of coral versus macroalgal dominance. However, it is unclear how dispersal of coral and macroalgae among reefs might impact this bistability and the resilience of the coral-dominated state. We develop a mathematical model to investigate how reef cover dynamics...
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... In reefs worldwide, anthropogenic impacts have driven the loss of corals, promoting the expansion of rapid-growing organisms like macroalgae, zoanthids, and soft corals (Norström et al. 2009;Arias-González et al. 2017;Precht et al. 2020). Other reefs, such as those in the Brazilian Province, have a low abundance of hard corals, possibly due to natural environmental conditions that favor turf algae and zoanthids (Aued et al. 2018), but that still play an important role in favoring the occurrence of juvenile and adult reef fishes (Luza et al. 2022). ...
... Sessile competitors can use several mechanisms to outcompete hard corals, most requiring physical contact. Softbodied cnidarians, like soft corals and zoanthids, and some algae can disperse and dominate reef substrates due to their rapid asexual reproduction and high growth rates, often overgrowing hard corals (Suchanek and Green 1981;Benayahu and Loya 1985;Precht et al. 2020). Depending on their morphology, macroalgae can cause shading and abrasion on corals' tissue (McCook et al. 2001). ...
... Apart from their similarities in occupying space on the reef very quickly (Suchanek and Green 1981;Precht et al. 2020), macroalgae and zoanthids are different organisms with distinct evolutionary histories and ecological pressures. Also, their morphology and growth forms (D. delicatula is a foliose alga, while P. caribaeorum is an encrusting cnidarian) could imply in different effects on the corals. ...
Space can be limited in reef ecosystems leading to competitive interactions among sessile organisms. Some competitive mechanisms can require physical contact while others operate with proximity between organisms. We investigated how the scleractinian coral Siderastrea stellata and the hydrocoral Millepora alcicornis respond to physical contact and proximity to the macroalga Dictyopteris delicatula and the zoanthid Palythoa caribaeorum, common pairs of interactions in Southwestern Atlantic reefs in Northeast Brazil. We held two colonies of the same species within the same tank, one in physical contact and the other within 5 cm of the competitor for four days with macroalgae and three days with the zoanthid. We monitored the corals for 26 days taking photographs and measuring their photosynthetic efficiency (PE) at the point of contact and on the side where competitors were in proximity. Corals were only affected when physically contacted by the competitors, with the macroalga causing a slight damage on M. alcicornis and almost no effect on S. stellata. Contacts with P. caribaeorum reduced the PE and caused tissue discoloration in both corals. M. alcicornis recovered after 26 days but the contacted areas of S. stellata remained discolored and with low PE. Macroalgae and zoanthids required physical contact to damage corals, with the zoanthid causing more damage than the macroalgae. These results suggest that if local and global stressors make corals weaker competitors (e.g. warming) or favor macroalgae and zoanthid growth (e.g. nutrients), corals could be replaced by either of these organisms affecting ecosystem structure and functioning.
... Herbivores' fundamental ecological roles are partly the result of their functional diversity (Table 11.1), which is still a developing research topic in the Caribbean (Adam et al. 2015a). For example, the long-spined sea urchin (Diadema antillarum Philippi, 1845) is considered an essential herbivore given its high densities and feeding rate (Ogden and Lobel 1978;Ogden and Carpenter 1987;Mumby et al. 2006;Precht et al. 2020). D. antillarum is a generalist herbivore that consumes turf-forming algae (e.g., red filamentous algae), upright fleshy (Dictyota sp.), leathery (Sargassum sp. and Lobophora sp.), calcareous algae (Galaxaura sp.), and even corals and other sessile invertebrates (Solandt and Campbell 2001;Herrera-Lopez et al. 2004). ...
Herbivory is an essential ecological process on coral reefs because it balances competition among benthic organisms such as corals and macroalgae. The geomorphological diversity of Cuban coral reefs and their distinctive protection levels present a unique opportunity to showcase the impacts of herbivory on reef dynamics. In this chapter we compiled information on the distribution and abundance of the essential reef herbivores (sea urchins and fishes) on the Cuban shelf and analyzed these data in light of reef characteristics and functioning (e.g., structure, benthic composition). We report an overall low (<1 Ind. m−2) presence of Diadema antillarum on the Cuban shelf and herbivorous fish biomass ranging from 11 g m−2 (La Habana) to 60 g m−2 (Jardines de la Reina), which may explain the overall high macroalgal abundance (47% cover). Our detailed review of Cuban reef literature reveals few studies addressing herbivory directly on coral reefs but many studies describing benthic and fish communities, which offer excellent potential for future studies. We describe two contrasting examples of herbivore effect on macroalgal communities and identify potential questions and research topics of interest for Cuba and the rest of the Greater Caribbean.
... Direct effects include increased mortality and decreased growth, fecundity, and recruitment of corals (McCook, Jompa & Diaz-Pulido, 2001;Box & Mumby, 2007;Rasher & Hay, 2010;Fong & Paul, 2011;Donovan et al., 2021). Indirect effects include the loss of suitable substrate for recruitment of corals and other sessile organisms, further impeding recovery of coral reefs (Kuffner et al., 2006;Ritson-Williams et al., 2009;Precht et al., 2020). Increased macroalgal cover and biomass in combination with declines in coral cover have persisted in modern surveys in most locations (Jackson et al., 2014;De Bakker et al., 2017). ...
... Although many coral reefs remain in decline, there have been some positive changes in herbivore populations. Some areas have seen increases in D. antillarum, and these increases have been linked to lower macroalgal cover (ranging from 5-10 times lower) and increases in coral cover and recruitment (2-10 times higher) (Edmunds & Carpenter, 2001;Idjadi, Haring & Precht, 2010;Kramer et al., 2015;Precht et al., 2020). Along with increases in D. antillarum, increased prevalence of marine protected areas and bans on fishing herbivorous fishes have been linked to increases in both biomass and density of herbivorous fish, which in some areas has led to decreases in macroalgae (Halpern, 2003;Jackson et al., 2014;Edwards et al., 2014;McField et al., 2020;Mumby et al., 2021). ...
... Some areas have seen increases in D. antillarum, and these increases have been linked to lower macroalgal cover (ranging from 5-10 times lower) and increases in coral cover and recruitment (2-10 times higher) (Edmunds & Carpenter, 2001;Idjadi, Haring & Precht, 2010;Kramer et al., 2015;Precht et al., 2020). Along with increases in D. antillarum, increased prevalence of marine protected areas and bans on fishing herbivorous fishes have been linked to increases in both biomass and density of herbivorous fish, which in some areas has led to decreases in macroalgae (Halpern, 2003;Jackson et al., 2014;Edwards et al., 2014;McField et al., 2020;Mumby et al., 2021). The effect of simultaneous D. antillarum and herbivorous fish recovery is not well understood. ...
On Caribbean coral reefs, losses of two key groups of grazers, herbivorous fishes and Diadema antillarum, coincided with dramatic increases in macroalgae, which have contributed to decreases in the resilience of these coral reefs and continued low coral cover. In some locations, herbivorous reef fishes and D. antillarum populations have begun to recover, and reductions in macroalgal cover and abundance have followed. Harder to determine, and perhaps more important, are the combined grazing effects of herbivorous fishes and D. antillarum on the structure of macroalgal communities. Surprisingly few studies have examined the feeding preferences of D. antillarum for different macroalgal species, and there have been even fewer comparative studies between these different herbivore types. Accordingly, a series of in-situ and ex-situ feeding assays involving herbivorous fishes and D. antillarum were used to examine feeding preferences. Ten macrophytes representing palatable and chemically and/or structurally defended species were used in these assays, including nine macroalgae, and one seagrass. All species were eaten by at least one of the herbivores tested, although consumption varied greatly. All herbivores consumed significant portions of two red algae species while avoiding Halimeda tuna, which has both chemical and structural defenses. Herbivorous fishes mostly avoided chemically defended species while D. antillarum consumed less of the structurally defended algae. These results suggest complementarity and redundancy in feeding by these different types of herbivores indicating the most effective macroalgal control and subsequent restoration of degraded coral reefs may depend on the recovery of both herbivorous fishes and D. antillarum.
... In many cases, geohistorical studies not only document species declines that predate modern biomonitoring efforts but can provide estimates of the natural range of variability, which can then be used to gauge the significance of human-induced decimations. For example, the decline in the diversity and percent cover of reef corals induced by pollution, heat stress, overfishing, and acidification are well-documented (Jackson et al., 2001;Pandolfi et al., 2003;Aronson and Precht, 2006;Precht et al., 2020). But how do they compare to natural variability in coral cover? ...
Near-time conservation palaeobiology uses palaeontological, archaeological and other geohistorical records to study the late Quaternary transition of the biosphere from its pristine past to its present-day, human-altered state. Given the scarcity of data on recent extinctions in the oceans, geohistorical records are critical for documenting human-driven extinctions and extinction threats in the marine realm. The historical perspective can provide two key insights. First, geohistorical records archive the state of pre-industrial oceans at local, regional and global scales, thus enabling the detection of recent extinctions and extirpations as well as shifts in species distribution, abundance, body size and ecosystem function. Second, we can untangle the contributions of natural and anthropogenic processes by documenting centennial-to-millennial changes in the composition and diversity of marine ecosystems before and after the onset of major human impacts. This long-term perspective identifies recently emerging patterns and processes that are unprecedented, thus allowing us to better assess human threats to marine biodiversity. Although global-scale extinctions are not well documented for brackish and marine invertebrates, geohistorical studies point to numerous extirpations, declines in ecosystem functions, increases in range fragmentation and dwindling abundance of previously widespread species, indicating that marine ecosystems are accumulating a human-driven extinction debt.
... During the past few decades, coral reefs have been declining across the Caribbean region at unprecedented rates (Pandolfi et al. 2003;Tebbett et al. 2023). Propelled by the regional collapse of Caribbean acroporids (Acropora palmata and A. cervicornis) and the massive die-off of Diadema antillarum, an important herbivore that reduces algae that competes with coral, recurring coral epizootic and massive bleaching events, coral reefs have undergone rapid transitions from benthic communities dominated by scleractinian corals to alternative states where macroalgae, sponges, and cyanobacterial benthic mats (CBM) have become the major components of Caribbean benthic communities (De Bakker et al. 2017;Precht et al. 2020;Tebbett et al. 2023). The impacts of such a rapid change are well-documented, bringing about a series of cascading events driven by loss of structural complexity, reef flattening and the concomitant reduction of biodiversity (Perry and Alvarez-Filip 2018), functional redundancy (Micheli et al. 2014) and, therefore, loss of reef resilience (Mora et al. 2016). ...
... caRiBBean JouRnal oF science [Volume 53 global and local stressors occurring individually and/or simultaneously across the region (Precht et al. 2020). For example, ocean warming events in 2005 and 2010 triggered severe bleaching events that have produced significant loss of live coral cover of major reef-building coral species (Eakin et al. 2010) while prompting corals to become more vulnerable to coral disease epizootic events (Croquer and Weil 2009). ...
Caribbean coral reefs have been declining at unprecedented rates, with about 50% of live coral cover lost over the past 50 years. The description of benthic and associated fish assemblages in remote areas, supposedly less vulnerable to human stressors, is necessary to better understand the spatial extent of declining trends, and to target areas for special management and protection. We present results from an expedition to Silver Bank (SiBa), Dominican Republic, aimed at providing the first quantitative assessment of benthic and fish assemblages in the area in the last 20 years. In April 2022, seven sites were surveyed using the Global Coral Reef Monitoring Network and the Atlantic Gulf Rapid Reef Assessment protocols, to determine benthic composition, coral richness, prevalence of diseases, invertebrates, and fish assemblages. Contrary to our expectations, reefs showed severe signs of deterioration, with coral cover seldom exceeding 11% on average, with no more than 14 species (from the more than 60 for the Caribbean region). Turf algae and macroalgae dominated the reefs (37–90%). Coral disease prevalence did not exceed 1–2%, and no evidence of epizootic Stony Coral Tissue Loss Disease (SCTLD) was noticed. Clear signs of overfishing were recorded, with carnivores above 15 cm being scarce across all sites. Furthermore, herbivorous species also depicted sizes below 15 cm, with no more than eight species. Our results change the previous conception that reefs at Silver Bank are healthier than coastal reefs because they benefit from low anthropogenic pressures. This serves as an alert to local environmental authorities to improve surveillance and management actions to preserve this area.
... The rise of alternative stable states to coral dominance has been attributed to several processes that contribute to reductions in coral cover and the increase of macroalgae. Besides the release of topdown control of macroalgae due to overfishing, bottom-up nutrient enrichment of macroalgae as a result of eutrophication and side-in perturbations directly affecting coral, such as diseases, predator outbreaks, thermal and sedimentation stress, and natural disasters are also a cause of coral demise (Precht et al. 2020). When multiple impacts are in place, measuring the causes of coral cover reductions and predicting the trajectories of dominant taxa on tropical reefs is a complex task, and it is still a matter of debate how extensive and persistent the macroalgal dominance is (see Jackson et al. 2014 andPrecht et al. 2020 for opposing views of the Caribbean region). ...
... Besides the release of topdown control of macroalgae due to overfishing, bottom-up nutrient enrichment of macroalgae as a result of eutrophication and side-in perturbations directly affecting coral, such as diseases, predator outbreaks, thermal and sedimentation stress, and natural disasters are also a cause of coral demise (Precht et al. 2020). When multiple impacts are in place, measuring the causes of coral cover reductions and predicting the trajectories of dominant taxa on tropical reefs is a complex task, and it is still a matter of debate how extensive and persistent the macroalgal dominance is (see Jackson et al. 2014 andPrecht et al. 2020 for opposing views of the Caribbean region). Nevertheless, the loss of coral cover is a worldwide trend that has risen in recent decades; estimates are that corals currently cover about 50−75% less of the substrate than they did in the past (Gardner et al. 2003, Bruno & Selig 2007, Bruno et al. 2009, Schutte et al. 2010, De'ath et al. 2012, Jackson et al. 2014, Hughes et al. 2018, and they have been replaced by macroalgae more often than by any other sessile organism (Norström et al. 2009, Jackson et al. 2014. ...
Overfishing of large herbivorous fishes is connected to the rise of algal-dominated states on coral reefs. The recovery of their populations is challenging, and future herbivore assemblages may be composed of smaller fish. With fisheries now targeting these smaller-sized herbivore populations, coral reef benthic communities may face unknown outcomes. We performed caging experiments in algal-dominated reefs of Northeastern Brazil, that have been depleted of large herbivorous fishes, to appraise the effects of removing small herbivores on benthic community composition and succession. Full cages simulated herbivore removal, and partial cages and open plots functioned as controls. In total, 36 experimental plots were monitored for 1 yr, accounting for the influence of seasonal changes in local conditions of temperature and turbidity. Overall macroalgal cover did not change between experimental treatments, but filamentous algae increased 5-fold inside full cages by the end of the experiment, surpassing articulated coralline forms as the dominant group. Higher temperatures during the dry season promoted filamentous algae when the top-down control of the herbivores was removed, while a reverse pattern was observed when fishes were allowed to feed inside plots. Small herbivores accelerated benthic succession, facilitating the dominance of articulated coralline algae as the climax community. Our findings oppose previous studies performed at sites with high abundances of large-bodied fishes, where herbivory decreased overall macroalgal cover, promoted filamentous and crustose coralline algae and delayed community succession. The further depletion of smaller-bodied herbivores can trigger shifts in benthic community dynamics that interact with water temperature, which may have implications for reef resilience in an ocean-warming scenario.
... Coral reefs are in decline worldwide in large part due to the compounding effects of a variety of global and local stressors including increases in nutrients from anthropogenic and natural sources, increases in open substrate due to coral mortality, and decreases in herbivory (Burke et al., 2011;Fong and Paul, 2011;Hughes et al., 2017;Roff and Mumby, 2012). On Caribbean coral reefs, a major consequence of these stressors is a high abundance of macroalgae, a low abundance of corals, and, in some areas, a shift to an algal-dominated system (Mumby et al., 2007;Precht et al., 2020). Decreases in herbivory can be linked to overfishing of herbivorous fishes, especially large-bodied parrotfishes, and the mass die-off of the long-spined sea urchin Diadema antillarum (Holbrook et al., 2016;Jackson et al., 2014;Shantz et al., 2020). ...
... Human impacts (e.g., overfishing, pollution) acting synergistically with natural processes (e.g., ocean warming, more intense and frequent hurricanes) have affected the resilience of coral reefs to respond to present and future impacts (Hughes et al., 2003(Hughes et al., , 2010(Hughes et al., , 2018. Particularly, the Caribbean coral reefs have suffered notorious damage during the last centuries, e.g., coral-to-macroalgae shifts in dominance, a decrease in predators and herbivorous fish abundance (Hughes, 1994;Paddack et al., 2009;Jackson et al., 2014;Precht et al., 2020). ...
Marine protected areas (MPAs) have been implemented on coral reefs as management and conservation tools since coral reefs provide significant ecological and economic values. For instance, Punta Francés National Park (PFNP) constitutes one of the most pristine marine environments in the Cuban archipelago, where recreational SCUBA diving has long been the most important activity. The goods and services provided by this area, the gaps in its biodiversity knowledge, and the putative effect of the MPA, prompted this research aims (1) to characterize reef fish assemblages in the coral reef of Punta Francés and (2) to test the hypothesis that PFNP hosts more abundant and diverse fish assemblages than the adjacent non-protected reef due to the higher habitat heterogeneity and protection level inside the PFNP. We have organized the analysis into four parts: (1) taxonomic and functional variation of fish assemblages; (2) potential factors influencing fish assemblage structure; (3) representativeness of species with special concern; and (4) functional redundancy analysis. The study was carried out from 2011 to 2014 in three reef habitats (reef crest, reef slope, and spur and groove), both inside and outside the PFNP. We found no differences in species and functional composition of fishes between areas with different protection levels. However, reef fish assemblages depended heavily on habitat type, demonstrating the importance of reef slope and reef crest habitats. No strong mangroveseagrass bed-coral reef connection was evident for the ichthyofauna reported to use mangroves and seagrasses as nurseries. Low biomass and abundance of predatory species and fish families important to conservation is a concerning outcome. Some functional traits were represented by only one or very few species across the entire area, which likely compromised ecological function in the system. The most distressing issue was the non-consistent differences found between protected and non-protected areas, suggesting the necessity of reviewing the management objectives for reef fishes in PFNP and a clear need to update its management plan and perhaps its boundaries.
https://authors.elsevier.com/a/1gVIQ8MvAty0jQ
... Even though sea urchins recovered in some areas and cropped down algae, the macroalgal regime still prevails in many areas. While the exact contribution of top-down, bottom-up and "side-in" (disease, climate, etc.) mechanisms to the coral decline is still highly debated (Precht et al., 2020), the increase in macroalgae was undoubtedly caused by the preceding changes in the food web, gradually reducing top-down control. ...
... Long before conservation palaeobiology began to develop as a subdiscipline, palaeoecologists recognized that the fossil record of coral reefs provides a baseline with which to compare the situation on contemporary reefs (Jackson 1992;Pandolfi and Greenstein 1997;Pandolfi and Jackson 2006;Greenstein and Pandolfi 2008). Observations of historical constancy of coral assemblages during interglacial intervals (Jackson 1992;Pandolfi 1996;Precht 1997, 2006;Jackson et al. 2001;Precht et al. 2020), have led to controversy over the timing, mechanisms, and causality of both millennial-scale stasis and departures over the last half-century from those persistent, coral-dominated states (Precht and Aronson 2016;Bruno et al. 2019;Cramer et al. 2020). Other reef systems have proven to be dynamic over centuries to millennia, strongly suggesting a primary role for climate change in driving both the biogeography of coral taxa and spatiotemporal trends in reef development at those temporal scales (Precht and Aronson 2004;Greenstein and Pandolfi 2008;Toth et al. 2012Toth et al. , 2018Toth et al. , 2021Clark et al. 2018). ...
The uncemented reef-frameworks of Pacific Panamá, which have been dominated through the Holocene by branching corals of the genus Pocillopora , experienced a hiatus in vertical accretion lasting ∼2300 years, beginning ∼4100 years ago. The hiatus has been attributed to an increase in variability of the El Niño-Southern Oscillation (ENSO). We tested the alternative hypothesis that the hiatus was solely the result of bioerosion, assuming an acute disturbance halted coral growth 1800 years ago (the time at which reef accretion resumed after the hiatus) and that the entire framework remained in the taphonomically active zone at that time. We calculate that it would have taken 167-511 years for bioerosion to fully remove 2300 years-worth of framework growth under those circumstances. In fact, most of the reef-framework in Panamá is stabilized in sediment that prevents the activity of bioeroders; only the upper ∼1 m of open framework-several decades-worth of growth at most-would have been vulnerable to erosion, greatly increasing the time required to bioerode 2300 years of accumulation. We conclude that that the hiatus was not solely an artifact of bioerosion; rather, a long-term increase in ENSO variability suppressed coral growth and vertical reef accretion.
