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The nature of crustose coralline algae and their interactions on reefs
... Crustose coralline algae (CCA) play fundamental roles in the ecology and functioning of coral reefs, contributing to reef construction through cementation and consolidation of reef substrate and inducing coral larval settlement, thus facilitating reef resilience (Birkeland et al., 2021;Birrell et al., 2008;Gómez-Lemos et al., 2018;Johnson, 1961;Littler & Littler, 2013;Morse et al., 1994). The contribution of CCA to reef growth is underpinned by the precipitation of calcium carbonate in the thallus cell walls. ...
... It is likely that vertical calcium carbonate accretion (i.e., vertical growth) in the smooth crusts of P. antillarum occurs more consistently throughout the crust (although there is some variability), while in L. cf. kaiseri, growth seems to occur more rapidly in the protuberances (branches), which receive relatively more light (and possibly more nutrients) than regions of the thallus surrounding the base of protuberances (as suggested by Littler & Littler, 2013). We have also previously found that both species have similar rates of skeletal bioerosion (Ramírez-Viaña et al., 2021), but L. cf. ...
... As mentioned earlier, thallus protuberances in L. cf. kaiseri may receive relatively higher irradiance and nutrients (Littler & Littler, 2013) and less sediment accumulation (L. Pulecio-Plaza, personal observation) and are faster growing regions of the thallus. ...
Crustose coralline algae (CCA) are important components of reef ecology contributing to reef framework construction. However, little is known about how seasonal upwelling systems influence growth and calcification of tropical CCA. We assessed marginal and vertical growth and net calcification rates of two dominant but morphologically different reef-building CCA, Porolithon antillarum and Lithophyllum cf. kaiseri, in a shallow coral reef of the Colombian Caribbean during upwelling and non-upwelling seasons. Growth and calcification rates varied seasonally with higher values during the upwelling compared to the non-upwelling (rainy) season. Annual vertical growth showed rates of 4.48 ± 1.58 and 4.31 ± 2.17 mm · y-1 , net calcification using crust growth estimates of 0.75 ± 0.30 g and 0.68 ± 0.60 g CaCO3 · cm-2 · y-1 and net calcification using the buoyant weight method of 1.49 ± 0.57 and 0.52 ± 0.11 g CaCO3 · cm-2 · y-1 in P. antillarum and L. kaiseri, respectively. Seawater temperature was inversely related with growth and calcification; however, complex oceanographic interactions between temperature and resource availability (e.g., light, nutrients, and CO2 ) are proposed to modulate CCA vital rates. Although CCA calcification rates are comparable to hard corals, CCA vertical accretion is much lower, suggesting that the main contribution of CCA to reef construction is via cementation processes. These results provide baseline data on CCA in the region and generate useful information for monitoring the impacts of environmental changes on tropical upwelling environments.
... Sin embargo, el grupo más numeroso de algas rojas calcificadas es el de las algas coralinas que agrupa en el presente cerca de 800 especies (Woelkerling 1988;Guiry y Guiry, 2020). En las algas coralinas el carbonato cálcico ocurre bajo la forma de Mg-calcita como constituyente de la pared celular, lo que les permite construir estructuras sólidas y duraderas sustentando formaciones como los arrecifes tropicales o los lechos de rodolitos (Littler y Littler 2013). ...
... Este grupo de algas ha sido un componente constante de las comunidades marinas a lo largo del tiempo, lo que no solo permite seguir la historia de este grupo, sino que, además, son buenos referentes sobre los que establecer las condiciones ambientales del pasado (Rösler et al. 2017). Su protagonismo ha sido tan elevado que, por ejemplo, los hábitats costeros carbonatados del Mioceno presentan una facies de depósitos de algas coralinas que reemplazaron temporalmente a los corales como productores dominantes de carbonatos en trópicos y subtrópicos (Littler y Littler 2013). Su distribución, mantenida en el tiempo y a escala global, ha permitido detectar en el pasado tanto picos de diversidad como periodos de extinción (Aguirre et al. 2000). ...
... Estas algas han tenido un indudable éxito evolutivo y su diversificación revela la capacidad de este grupo para colonizar hábitats en un amplio rango de temperatura, luz y perturbaciones. Están presentes desde las regiones polares hasta las tropicales, alcanzando su mayor diversidad en los arrecifes, donde proporcionan cementación a los corales y pueden ser productores de arrecifes primarios (Littler 1972;Adey y Macintyre 1973;Adey 1998;Nelson 2009;Littler y Littler 2013). Considerado como un grupo exclusivamente marino muy escasamente representado en los hábitats salobres (Irvine y Chamberlain 1994), recientemente se han descubierto poblaciones estrictamente dulciacuícolas de un río de Croacia (Žuljević et al. 2016). ...
... Sin embargo, el grupo más numeroso de algas rojas calcificadas es el de las algas coralinas que agrupa en el presente cerca de 800 especies (Woelkerling 1988;Guiry y Guiry, 2020). En las algas coralinas el carbonato cálcico ocurre bajo la forma de Mg-calcita como constituyente de la pared celular, lo que les permite construir estructuras sólidas y duraderas sustentando formaciones como los arrecifes tropicales o los lechos de rodolitos (Littler y Littler 2013). ...
... Este grupo de algas ha sido un componente constante de las comunidades marinas a lo largo del tiempo, lo que no solo permite seguir la historia de este grupo, sino que, además, son buenos referentes sobre los que establecer las condiciones ambientales del pasado (Rösler et al. 2017). Su protagonismo ha sido tan elevado que, por ejemplo, los hábitats costeros carbonatados del Mioceno presentan una facies de depósitos de algas coralinas que reemplazaron temporalmente a los corales como productores dominantes de carbonatos en trópicos y subtrópicos (Littler y Littler 2013). Su distribución, mantenida en el tiempo y a escala global, ha permitido detectar en el pasado tanto picos de diversidad como periodos de extinción (Aguirre et al. 2000). ...
... Estas algas han tenido un indudable éxito evolutivo y su diversificación revela la capacidad de este grupo para colonizar hábitats en un amplio rango de temperatura, luz y perturbaciones. Están presentes desde las regiones polares hasta las tropicales, alcanzando su mayor diversidad en los arrecifes, donde proporcionan cementación a los corales y pueden ser productores de arrecifes primarios (Littler 1972;Adey y Macintyre 1973;Adey 1998;Nelson 2009;Littler y Littler 2013). Considerado como un grupo exclusivamente marino muy escasamente representado en los hábitats salobres (Irvine y Chamberlain 1994), recientemente se han descubierto poblaciones estrictamente dulciacuícolas de un río de Croacia (Žuljević et al. 2016). ...
La futura acidificación de los océanos tendrá un impacto generalizado en las especies marinas y los ecosistemas. Las algas coralinas (Corallinophycidae, Rhodophyta) son elementos conspicuos de las comunidades litorales en todas las latitudes. En la pared celular de las algas coralinas interviene la forma más soluble de calcita, lo que las hace particularmente vulnerables a variaciones en el pH del mar. En esta síntesis discutimos el actual conocimiento sobre las algas coralinas de Canarias en el contexto de los avances producidos en las últimas décadas tanto en la taxonomía (aplicación de diferentes criterios taxonómicos) como en la ecología (un grupo de organismos que prestan unos servicios ecosistémicos muy valiosos). En Canarias las algas coralinas están actualmente representadas por 56 especies, pero existen fundadas razones para creer que es una subestimación del número real de especies. Participan en la mayoría de las comunidades litorales y su abundancia permite considerarlas como elementos característicos de numerosos hábitats, algunos de ellos escasamente investigados.
... These algae are wide range geographical distribution that can be found from low to high latitude and from intertidal to depth area. In alive condition, these algae have pink-reddish color and categories as a marine plant (Phylum: Rhodophyta, Class: Florideophyceae, Subclass: Corallinophycidae, Order: Corallinales, Family: Corallinaceae) that attached on the substrate with rootlike called as holdfast (Littler and Littler, 2013;Nash et al., 2019). In the early description, the CCA divide into generic names because of their morphologies differences, a flat form knowing as Lithophyllum and a branched form as Lithothamnium (Littler and Littler, 2013). ...
... In alive condition, these algae have pink-reddish color and categories as a marine plant (Phylum: Rhodophyta, Class: Florideophyceae, Subclass: Corallinophycidae, Order: Corallinales, Family: Corallinaceae) that attached on the substrate with rootlike called as holdfast (Littler and Littler, 2013;Nash et al., 2019). In the early description, the CCA divide into generic names because of their morphologies differences, a flat form knowing as Lithophyllum and a branched form as Lithothamnium (Littler and Littler, 2013). McCoy and Kamenos (2015) have a different term for flat and branching form that referred as non-articulate (non-genicular) and articulate (genicular) respectively. ...
... CCA is dependent on light, only view of CCA reported growth and distributed limited from the non-euphotic zone. For instance, distribution of the deepest rhodoliths that was found in 295 m off San Salvador Seamount of Bahama, survive with dim light about 8.10 -2 μmol photons/ m 2 / s 1 , less diverse comparing with high sunlight irradiance in the upper-intertidal area (Littler and Littler, 2013). Photosynthesis is an important process of CCA growth or calcification. ...
Crustose coralline algae (Corallinophycideae) are red algae that produced calcium carbonate and are well recognized as foundation species in the epipelagic zone of the marine ecosystem. These algae induced settlement juvenile of coral by released chemical cues from bacterial communities on the surface of their colonies. Their extracellular calcium carbonate also can stabilize reef structure that influencing many invertebrate attaches and growth in the seabed. Crustose coralline algae (CCA) have obtained attention because of their distribution and health compromise to increasing seawater temperature, ocean acidification, and pollutant. As a cryptic species in the ecosystem, the presence of CCA recruit sometimes doesn't have attention, especially on their capability to occupy the empty space. This study aimed to document coverage and number of CCA recruit in two different recruitment tile's material. The highest CCA percentage of the cover was showed inside surface than others surface in all stations. Light intensity and low sedimentation were suggested as a key factor of success of high coverage. Overall, station higher CCA recruits have shown from Tiga Warna. Low sedimentation and protection from aerial exposure became the main reason for it. No significant difference number of CCA recruits between marble and sandstone in this study. Successful CCA recruitment in this study can give a wide picture that natural recruitment of coral and other reef biodiversity in Southern Malang might be will succeed because of the abundance of coralline algae that support their life history stage.
... L'habitat influe également sur les taux de croissance des coraux nouvellement colonisés (Adjeroud et al. , 2010 (Babcock et Mundy 1996). Des recherches récentes sur l'influence de la microstructure des récifs sur le recrutement corallien ont montré que les refuges physiques améliorent considérablement le recrutement et la survie après implantation (Brock et al. 1979;Nozawa 2008;Doropoulos et al. 2016 (Littler et Littler, 2013). Les algues corallines des eaux profondes sont mal connues. ...
... Les algues corallines des eaux profondes sont mal connues. La distribution très large des algues corallines souligne leur grande contribution à la productivité, au réseau trophique marin, à la sédimentologie et à la biogenèse des récifs dans les mers tropicales (Littler et al. 1985;Steneck 1986 (Keats et al. 1997;Littler and Littler 2013). Dans les régions tropicales, les CCA construisent des crêtes algales (Steneck et al. 1997) et contribuent considérablement à la productivité primaire sur les récifs (Chisholm 2003). ...
... Certaines espèces de CCA induisent la métamorphose et la colonisation des coraux de récif (Harrington et al. 2004), tandis que d'autres espèces peuvent inhiber la colonisation des coraux (Ritson-Williams et al. 2009). Malgré leur omniprésence, la taxonomie, la biologie et l'écologie des algues corallines restent mal comprises, et elles sont souvent négligées ou intentionnellement ignorées par les scientifiques des récifs coralliens (Littler et Littler 2013). La taxonomie des algues corallines est en constante évolution, ce qui entrave les progrès des études écologiques. ...
Les algues corallines encroûtantes (CCA) sont communément associées à des récifs sains et jouent un rôle important dans les systèmes benthiques en guidant la colonisation de nombreux organismes, comme les coraux. Cependant, la capacité des CCA à induire l’implantation des coraux ne fonctionne pas pour toutes les espèces de CCA. Les larves de coraux sélectionnent certaines espèces d’algues, ce qui pose la question des mécanismes sous-jacents. Malgré l’énorme variété d’espèces de CCA dans les récifs, on en sait peu sur leur diversité chimique et microbienne et sur le rôle écologique de ces deux composants pour le recrutement des coraux. Le chapitre 2 étudie la composition microbienne et chimique de 6 espèces de CCA sur les récifs coralliens de Moorea, et comment ces deux compartiments sont liés au succès d’implantation des larves d’Acropora cytherea. Les résultats ont révélé que le taux d’implantation était le plus élevé sur l’espèce cryptique Titanoderma prototypum. Alors que toutes les espèces de CCA avaient des empreintes métaboliques distinctes et contenaient une grande diversité métabolomique, la diversité et la richesse métabolomiques de T. prototypum étaient plus élevées que celles des autres espèces. T. prototypum hébergeait également une diversité bactérienne plus élevée, et contenait une plus grande abondance de bactéries susceptibles de produire des composés antibactériens. Ces bactéries pourraient inhiber les agents pathogènes des coraux, ce qui pourrait à son tour améliorer la survie des larves. Ainsi, le recrutement corallien est un processus complexe de communications biochimiques entre les CCA, leurs communautés de surface microbiennes associées et les larves de coraux. Malgré la large acceptation que certaines espèces de CCA influencent positivement le recrutement corallien, il n’y a pas de données expérimentales sur les effets des espèces de CCA sur la survie et la croissance post-implantation tardive des coraux. Le chapitre 3 teste l’impact de 4 espèces de CCA, de deux types d’habitats (exposés et subcryptiques), sur la survie et la croissance des recrues de Pocillopora. Les CCA ont eu un effet contrasté sur la survie des recrues coralliennes suivant l’habitat et de la taille des recrues. Dans les habitats subcryptiques, les CCA réduisaient la survie et/ou la croissance des recrues coralliennes via la compétition directe, tandis que, dans les habitats exposés, elles amélioraient le recrutement des coraux en atténuant la concurrence avec le gazon algal. Cette étude a démontré que toutes les espèces de CCA ne sont pas bénéfiques à la survie et à la croissance des recrues coralliennes et qu’il existe une variabilité considérable dans l’issue et le processus de compétition entre les CCA et les coraux. Chapitres 4 et 5 déterminent si deux facteurs de stress environnementaux, respectivement l’acidification des océans (AO) et l’hypoxie, affectent l’association corail-CCA en perturbant le comportement et l’implantation des larves des deux espèces de coraux (A. cythera et A. pulchra), ainsi que leur recrutement, sur une espèce de CCA appropriée. Les larves des deux espèces évitaient l’exploration et l’implantation dans des environnements à faible pH ou à oxygène réduit. Ces résultats indiquent que les zones à faible teneur en oxygène et pH peuvent influencer négativement le succès d’implantation des larves de coraux et que l’oxygène et le pH peuvent être des signaux chimiques pour l’orientation et l’implantation des larves de coraux. Cette thèse aide à mieux comprendre le rôle des CCA, des micro-organismes et des composés chimiques dans la dynamique à petite échelle du recrutement des coraux maintenant et dans les conditions océaniques futures. Les résultats soulignent que les interactions CCA-corail sont des processus complexes qui sont probablement médiés par des composés chimiques et microbiens et que ces interactions peuvent être affectées par des environnements changeants.
... Examples include the Mediterranean Sea (Ballesteros, 2006;Langar et al., 2011), Bermuda in the northwest Atlantic Ocean (Ginsburg & Schroeder, 1973), Norway in the North Sea (Freiwald, 1998), and Taiwan in the northwest Pacific Ocean (Dai et al., 2009;Liou et al., 2017). Crustose coralline algae are well known as reef-building coralline algae and are located extensively in coral reefs, rocky shores, and shallow sea basins worldwide (Adey, 1978;Bosence, 1983;Chisholm, 2003;Cornwall et al., 2023;Costa et al., 2019;Littler & Littler, 2013). Coralline algae, like most calcified macroalgae, undergo calcification while also performing photosynthesis. ...
... The reef-forming species observed in the XAR are different from those in other reef regions having CCA sediment (Adey, 1975;Langar et al., 2011;Teichert, 2024). The genera Lithophyllum, Lithothamnion, Mesophyllum, Neogoniolithon, and Porolithon are commonly observed in CCA reefs around the tropical and subtropical regions in the Pacific and Atlantic Oceans (Adey, 1975;Adey & Macintyre, 1973;Littler & Littler, 2013;Teichert, 2024). In temperate regions, Lithophyllum and Lithothamnion are dominant components of the coralligenous concretions formed by an accumulation of calcified and encrusting algae growing in dim light conditions in Mediterranean benthic environments (Ballesteros, 2006). ...
The composition and abundance of crustose coralline algae (CCA) have been documented in the Xinfeng algal reef (XAR). Eight CCA species were identified, including four in Phymatolithon ( P. margoundulatum , P. taiwanense , P. variabile , and Phymatolithon sp.) and four only identified to the genus level ( Chamberlainium sp. and three Dawsoniolithon spp.). Chamberlainium sp. was the most abundant species, while the three species of Dawsoniolithon were rarely observed. The CCA coverage varied from 18% ± 15% to 27% ± 21% in spring seasons of 2021–2024, but there were no significant differences. Based on carbon‐14 dating, the CCA sediments in the XAR were estimated to be 5850–5990 years old. These CCA sediments were primarily composed of two paleo‐CCA species, resembling modern Chamberlainium sp. and Dawsoniolithon sp. 1. However, the modern species of Phymatolithon , which are widespread and abundant in the algal reefs of northwestern Taiwan, were not observed in the CCA sediments. It is unclear whether their absence was due to fragile thalli after their death or their lack of occurrence, and this requires further investigation. The paleoenvironmental data and biogenic sediment composition analysis suggests that the XAR started to develop ~6000 years ago when the sea surface temperature began to decrease and seawater turbidity increased due to rainfall. Additional CCA sediment samples from this algal reef are needed to fully understand the historical changes in the paleo‐environments in the XAR.
... Healthy coral reefs are often characterized by a high cover of both crustose coralline algae (CCA) and reef-building corals [6] and the abundance of these two types of organisms can be interdependent. In healthy coral reef ecosystems, CCA aid in reef accretion and stabilization by cementing loose rubble and sediment [7]. This function can be especially critical in areas exposed to disturbances that cause coral mortality and/or fragmentation of carbonate reef structures. ...
... CCA also provide hard substrate conducive to successful coral recruitment and emit cues that induce coral larval settlement [8][9][10][11]. In addition to the direct relationships between CCA and corals, CCA also create habitat for other organisms and are important settlement substrata for a number of other marine invertebrates [7]. ...
... CCA are marine multicellular plants with a calcified cell wall, largely composed of magnesium calcite (and occasionally, aragonite) crystals. They are composed of three thallii, which produce heavily calcified plates: the epithallus, the photosynthetic perithallus and the basal hypothallus (Littler and Littler 2013). Their red or pinkish coloration is due to the presence of pigments such as phycocyanin and phycoerythrin. ...
... Eggs are then brooded within the plant (Santelices 2002). Species generally display a triphasic life cycle composed of a haploid gametophyte stage, a diploid sporophyte and a second spore-forming stage (Littler and Littler 2013). ...
Brazilian reef environments are composed of a unique fauna. This chapter addresses the general biological and ecological aspects of 12 benthic reef-dwelling taxa found in Brazil: (i) scleractinian corals, which are primary reef-builders that produce the tridimensional framework; (ii) calcified hydrozoans belonging to the Millepora genus; (iii) other cnidarians such as octocorals, zoanthids and anemones; (iv) crustose coralline algae, which are also major reef-builders that produce extensive rhodolith beds; (v) bryozoans and (vi) vermetid gastropods, which have contributed significantly to reef-building in the Abrolhos Bank and Rocas Atoll, respectively; (vii) echinoderms, with emphasis on sea urchins, that control algal overgrowth through herbivory but may also contribute to bioerosion; (viii) sponges, which are abundant in Brazilian reefs and both add structural complexity and recycle organic matter, but also contribute to reef erosion; (ix) polychaetes and (x) mollusks, both of which may occasionally contribute to reef accretion and also engage in burrowing and erosion; (xi) crustaceans, which interact with numerous taxa and form multiple trophic links; and (xii) ascidians, a diverse cryptic dweller of the reef matrix. The basic morphology is presented for each taxon, as well as their diversity, reproductive biology and main functional roles.
... Calcareous red algae belonging to the group Rhodophyta are a group of coralline algae known widely for their ecological role as ecosystem engineers 3,4,5,6 . Among them, the nongeniculate coralline shows a worldwide distribution from tropical to polar Regions 14 . They are also one of the deepest occurring marine algae occurring from the intertidal regions to a depth exceeding 200 m 15 . ...
... In tropical reefs, they are known to construct algal ridges 26 and contribute significantly to primary productivity 7 . By cementing them, they are known to bond the reef together 14,20 . CCA is also known to induce larval settlement in various marine invertebrates 8,12,19,23,24 . ...
Crustose coralline algae (CCA) are calcareous red algae belonging to the diverse group Rhodophyta. They are known to play numerous important ecological roles in the coral reef ecosystems such as various invertebrate larval settlement, cementing the reef together, participating effectively in primary productivity. One of the most important ecological roles these algae play, are the settlement and metamorphosis of coral larvae. Though lots of observations have been made on a juvenile coral being settled on CCA, there has not been any study on the initial settlement of coral larvae on CCA. The present study was carried out in the intertidal regions of South Andaman district. During intertidal survey, a single thin layered CCA was observed to house four different coral recruits which had settled and metamorphosed to form a single polyp coral.
... The second group comprises species with branched thalli, that is, having numerous elongated protuberances or vertical columns. In the Indo-Pacific Ocean, branched Porolithon specimens have been variously referred to as either one species, P. gardineri (type locality: Coetivy Reef, Chagos Archipelago, Mauritius), or two species, P. craspedium (type locality: Onotoa, Gilbert Islands, Kiribati) and P. gardineri (Dawson, 1957;Kato et al., 2011;Littler & Littler, 2013;Payri & N'Yeurt, 1997;Santelices & Abbott, 1987;South & Skelton, 2003;Taylor, 1950;Tsuda, 2003;Tsuda & Fisher, 2012;Tsuda & Walsh, 2013). A partial rbcL gene sequence from the type specimen of P. gardineri was analyzed recently and shown to be distinct from other species of Porolithon, including P. coarctatum, which had been considered its synonym (Richards et al., 2021). ...
... Finally, given the ecological significance of Porolithon species that grow abundantly along shallow reef margins and that cement reef frameworks (e.g., Adey, 1978a;Johnson, 1961;Littler & Littler, 2013) and induce settlement of coral larvae (Diaz-Pulido et al., 2010;Heyward & Negri, 1999), it is important that the taxonomy of this genus is clarified. This is particularly important when considering the several synonymies previously suggested. ...
Porolithon is one of the most ecologically important genera of tropical and subtropical crustose (non‐geniculate) coralline algae growing abundantly along the shallow margins of coral reefs and functioning to cement reef frameworks. Thalli of branched, fruticose Porolithon specimens from the Indo‐Pacific Ocean traditionally have been called P. gardineri , while massive, columnar forms have been called P. craspedium . Sequence comparisons of the rbc L gene both from type specimens of P. gardineri and P. craspedium and from field‐collected specimens demonstrate that neither species is present in east Australia and instead resolve into four unique genetic lineages. Porolithon howensis sp. nov. forms columnar protuberances and loosely attached margins and occurs predominantly at Lord Howe Island; P. lobulatum sp. nov. has fruticose to clavate forms and free margins that are lobed and occurs in the Coral Sea and on the Great Barrier Reef (GBR); P. parvulum sp. nov. has short (<2 cm), unbranched protuberances and attached margins and is restricted to the central and southern GBR; and P. pinnaculum sp. nov. has a mountain‐like, columnar morphology and occurs on oceanic Coral Sea reefs. A rbc L gene sequence of the isotype of P. castellum demonstrates it is a different species from other columnar species. In addition to the diagnostic rbc L and psb A marker sequences, the four new species may be distinguished by a combination of features including thallus growth form, margin shape (attached or unattached), and medullary system (coaxial or plumose). Porolithon species, because of their ecological importance and sensitivity to ocean acidification, need urgent documentation of their taxonomic diversity.
... For this, focus should be directed towards the semantics of the word "mesophotic", which refers to intermediate light conditions, and on the variable nature of the distribution of photosynthetic benthic communities along the entire depth gradient, where light levels encompass five orders of magnitude, from z100% on the surface to z0.01%. By excluding the extremes of this variability (shallow areas where coral reefs could develop from z100% to z10%; and the deeper "photic" zone, which ranges from z0.1% to z0.01%, where crusty coralline algae have been reported [32,54], the mesophotic zone for the establishment of MCEs or MEs prevails as the intermediate light zone for benthic marine photosynthesis and primary production ( Figure 8). This image only shows the mesophotic boundaries based on optical depths, that should be the same worldwide. ...
... ture of the distribution of photosynthetic benthic communities along the entire depth gradient, where light levels encompass five orders of magnitude, from z100% on the surface to z0.01%. By excluding the extremes of this variability (shallow areas where coral reefs could develop from z100% to z10%; and the deeper "photic" zone, which ranges from z0.1% to z0.01%, where crusty coralline algae have been reported [32,54], the mesophotic zone for the establishment of MCEs or MEs prevails as the intermediate light zone for benthic marine photosynthesis and primary production ( Figure 8). This image only shows the mesophotic boundaries based on optical depths, that should be the same worldwide. ...
The distinction between shallow coral reefs and mesophotic coral ecosystems (MCEs) has not been fully clarified yet. The original definition of MCEs, by depths of 30–150 m, fixes their bathymetrical limits and fails to accommodate environmental and biological variation. Recent studies have indicated that water transparency and light availability may explain why MCEs do not occur at fixed depths but vary among localities. This study aimed to evaluate the presence and distribution of MCEs, along the central coast of Oaxaca, through optical depths and the associated benthic community. Using MODIS-Aqua satellite data (Kd490), we estimated the mesophotic optical depths monthly (z10%, z1%, z0.1%), over the last four years. In addition, to characterize benthic community structure, we conducted underwater photo quadrat surveys at two locations on the southern Mexican Pacific coast from 10 to 55 m depth. Significant differences between depths and locations were found in benthic communities. Furthermore, the lower distribution of photosynthetic taxa was different between the two locations but indicative to the z10% and z1% in both cases. Those differences were associated with the upwelling season, which reduces, drastically and differentially, the light availability for benthic communities between the two locations and limits the development of MCEs on the central coast of Oaxaca.
... The genus Amphiroa is important coralline algae in many shallow, near-shore exposed and tide-pool environments (Wai, 2018), which may experience different light intensities due to their distribution depth. They can fill the crevices in the reef structure and provide sand to the shore line via their calcified structures (Littler and Littler, 2013). Moreover, several species induce larval metamorphoses of Haliotis asinina (Williams et al., 2008). ...
... Frontiers in Marine Science frontiersin.org reef cementation (Nelson, 2009;Littler and Littler, 2013;Teichert et al., 2020). They are widely distributed from the tropics to polar latitudes and from intertidal zone to deeper water levels (Nelson, 2009;Schubert et al., 2020). ...
Coralline algae, an important calcifying group, play vital roles in the primary productivity, reef frameworks construction, and carbon store. In this study, we investigated the responses of an articulated coralline alga Amphiroa cf. fragilissima to ocean warming under various light intensities. The relative growth rate significantly decreased under light or heat stress. When A. cf. fragilissima was exposed to high light intensity (120 μmol photons m⁻² s⁻¹) at 32°C, the relative growth rate was lowest, which reduced by 87% compared with that of group A1 (60 μmol photons m⁻² s⁻¹, 26°C). Meanwhile, a higher level of algal bleaching occurred when light intensity was 120 μmol photons m⁻² s⁻¹. Similarly, Fv/Fm and Chl-a content were negatively affected by light and heat stress, but they were more affected by light. Furthermore, the mineralogical responses to temperature and light were investigated. The net calcification rate declined from 92.27 (60 μmol photons m⁻² s⁻¹, 26°C) to 10.92 μmol CaCO3 g⁻¹ DW day⁻¹ (120 μmol photons m⁻² s⁻¹, 32°C). High temperature significantly decreased Ca content in live algal pigmented layer, whereas there were no significant differences in Ca content in the skeleton layer, implying that the pigmented layer could protect skeleton layer from mineral changes under ocean warming. The results revealed that A. cf. fragilissima was impaired by high light or thermal stress from various aspects, including growth, survival, photosynthesis, reproduction, and calcification. This study contributes to understand the effects of warming and light on coralline algae and provides a theoretical basis to protect the richness and diversity of calcified macroalgae.
... Moreover, CCA also play a role of a stabilizer of substrates in the reef system and with coral as the primary carbonate source in the coral reef ecosystem [22]. Another researcher revealed that CCA constitute an energy source for many reefs biotas such as Diadema urchins, scariids, surgeonfish, and other invertebrates [23]. ...
... CCA are red algae that belong to the division of Rhodophyta and order of corallines. These algae have carbonate thalli with red or pink colors that are very easy to distinguish from coral [23]. These algae also have unique growth forms such as shelf-like crusts, upright branches, and thick knobby crusts. ...
Crustose Coralline Algae (CCA) are known as one of the calcifying algae which have important ecological responsibility on coral reef thus attracting coral juvenile, unstable binding substrate, source of food, and creating a substrate for some invertebrates. However, the study on the life histories of these algae was very poor when compared with coral. South Malang, East Java, directly faces the Indian Ocean and has a spatial coral reef ecosystem scattered in many places, one of the Nature Reserve Pulau Sempu (NRPS). This study aimed to get information regarding CCA recruitment and their growth strategy in plate materials. We used two different tile materials (settlement plates) composed of silica and carbonate base. The research result showed that CCA adhered Palimanan stone that contained more silica. The position also defined CCA recruitment because horizontal position is more calcified than the horizontal one. This research demonstrated the availability of CCA juveniles to succeed in their recruitment process and gave hope to the coral recruitment coral in Nature Reserve Pulau Sempu put over in substrate with coated CCA.
... Two algal functional groups that are sometimes pooled in reef benthic studies, yet have distinct ecological roles, are the crustose coralline algae (CCA) and the algal turfs. CCA are encrusting, calcifying red algae that stabilize the reef framework and support structural complexity (Teichert et al., 2020;Littler and Littler, 2013;Steneck, 1986). They also contribute to carbonate production, possibly more so than reef-building corals (Cornwall et al., 2023). ...
Coral reef algae serve many important ecological functions, from primary production to nutrient uptake and reef stabilization, but our knowledge of longer-term effects of thermal stress on algae in situ is limited. While ocean warming can facilitate proliferation of algae and potential phase shifts from coral to macroalgal-dominated states, algal responses may vary by species, genus, functional group, or type (e.g., calcareous vs. fleshy). We used 11 years of annual monitoring data (2009-2019) that spans two El Niño-associated heatwaves to examine benthic algal community dynamics on Palmyra Atoll in the central Pacific Ocean. We quantified the percent cover of algal taxa via image analysis of permanent benthic photoquadrats from two habitats on Palmyra: the deeper, wave-exposed fore reef (10 m depth) and the shallower, wave-sheltered reef terrace (5 m depth). Each habitat was characterized by distinct algal communities: predominantly calcareous taxa on the fore reef and predominantly fleshy taxa on the reef terrace. Patterns in abundance fluctuated over time and/or in response to thermal anomalies in 2009 and 2015. Fleshy algae generally increased in cover post-warming, which coincided with large declines of the calcified macroalgae, Halimeda spp. Long-term monitoring of coral reef algal communities is critical for understanding their differential responses to thermal stress and can improve projections of ecosystem functioning in the context of global change.
... This differentiation is critical, as increases in macroalgal biomass can break key ecological feedbacks, further suppressing the recovery of coral populations (e.g., Hoey and Bellwood 2011;Van de Leemput et al. 2016;Johns et al. 2018). In contrast, CCA's are a critical component of healthy reef ecosystems, contributing to reef calcification and stabilisation of the reef framework (e.g.,Teichert et al. 2020;Cornwall et al. 2023), promoting the settlement and survival of coral larvae (e.g.,Harrington et al. 2004;Abdul Wahab et al. 2023), and inhibiting the settlement and colonisation of fleshy fouling organisms(Littler and Littler 2013). Current levels of coral cover on central CSMP reefs (mean: 12.2%; range: 5.8-24.1%) ...
The Coral Sea is a critically important and significant ecosystem, which (like coral reefs globally) is increasingly threatened by changing environmental conditions, particularly ocean warming. Previous surveys (2020-2022) of shallow reef habitats across the Coral Sea Marine Park (CSMP) documented widespread and severe bleaching of corals in 2020 and 2021. These back-to-back bleaching events led to a substantial (52%) decline in coral cover in shallow (<15m depth) reef habitats throughout the CSMP.James Cook University was commissioned by Parks Australia to assess:(i) the latest condition of benthic, fish and invertebrate communities within the CSMP;(ii) any ongoing impacts of the back-to-back (2020 and 2021) bleaching events on benthic, fish and invertebrate communities; and(iii) gain some understanding of the resilience and biodiversity of the CSMP ‘brightspot’ reefs.
... If corals do not contribute to reef accretion as much as previously assumed, other organisms may underpin reef accretion. Crustose coraline algae (CCA), for example, have been shown to be key secondary reef builders, able to consolidate and cement reef framework (Littler and Littler 2013), thus playing an important role in reef accretion . Kench et al. (2022) showed that vertical reef accretion in the low coral cover wave breaking zone (reef crest) was maintained, even shortly after periods of elevated sea-surface temperatures, by CCA calcification. ...
... This differentiation is critical, as increases in macroalgal biomass can break key ecological feedbacks, further suppressing the recovery of coral populations (e.g.,Hoey and Bellwood 2011;Van de Leemput et al. 2016;Johns et al. 2018). In contrast, CCA's are a critical component of healthy reef ecosystems, contributing to reef calcification and stabilisation of the reef framework (e.g.,Teichert et al. 2020;Cornwall et al. 2023), promoting the settlement and survival of coral larvae (e.g.,Harrington et al. 2004;Abdul Wahab et al. 2023), and inhibiting the settlement and colonisation of fleshy fouling organisms(Littler and Littler 2013).Current levels of coral cover on central CSMP reefs (mean: 10.0%; range: 6.0-19.0%) are generally greater than that of historical surveys of isolated bommies within the lagoons at Herald Cays, Chilcott Islet and LihouReef (1-5% in 2003Reef (1-5% in to ~6% in 2007 ...
In responding to a tender from Parks Australia, a team of researchers representing the College of Science and Engineering at James Cook University (JCU) completed surveys of eleven reefs in the Coral Sea Marine Park.
The Coral Sea is a critically important and significant ecosystem, which (like coral reefs globally) is increasingly threatened by changing environmental conditions, particularly ocean warming. Indeed, previous surveys (2020-2022) of shallow reef habitats across the Coral Sea Marine Park (CSMP) documented widespread and severe bleaching of corals in 2020 and 2021. These back-to-back bleaching events led to a substantial (52%) decline in coral cover in shallow (<15m depth) reef habitats throughout the CSMP.James Cook University was commissioned by Parks Australia to assess:(i) the latest condition of benthic, fish and invertebrate communities within the CSMP;(ii) any ongoing impacts of the back-to-back (2020 and 2021) bleaching events on benthic, fish and invertebrate communities; and(iii) gain some understanding of the resilience and biodiversity of the CSMP ‘brightspot’ reefs.
... They are important reef stabilizers and builders, providing settlement substrates for corals, epiphytic organisms, and marine invertebrates [3][4][5], and providing habitat, refuge, and grazing areas for numerous other marine organisms [6]. NGCA are widely distributed from the tropical to the polar marine waters, and from the intertidal zone down to 295 m depths [7]. ...
Non-g eniculate coralline red algae (NGCA) provide habitats for many epiphytic fauna and flora, and are considered reef engineers. The identification of NGCA is challenging due to cryptic speciation and their phenotypic plasticity that can be mediated by environmental conditions. Using DNA sequence data (psbA gene), a systematic examination was undertaken of the diversity and abundance of NGCA from two different reef conditions (fair and poor reef) and depth zones (shallow and deep zone) of a subtidal reef in the Gulf of Thailand at Koh Taen, Surat Thani Province, Thailand. Phylogentic analysis revealed 11 putative species: Chamberlainium sp., Dawsoniolithon sp., Hydrolithon boergesenii, Lithophyllum sp.1, Lithophyllum sp.2, Neogoniolithon sp.1, Neogoniolithon sp.2, Parvicellularium sp., Sporolithon ptychoides, Sporolithon sp.1 and Sporolithon sp.2. Specimens attributed to a newly recorded genus Parvicellularium, showed its highest abundance in the deep zone, while specimens attributed to Lithophyllum and Sporolithon were dominant in the shallow zone. The abundance of all NGCA genera showed no significant differences among reef conditions. Here, we present an updated overview of the diversity and abundance of NGCA in Thai waters.
... They contribute significantly to the diversity of these habitats by providing substrates for the settlement of various benthic invertebrates (Daume et al., 1999;Heyward and Negri, 1999;Tebben et al., 2015;Weiss and Martindale, 2017;Duran et al., 2018). Their fundamental ecological functions include carbonate production, both in terms of bioconstructions and loose sediment (Steneck, 1986;Adey, 1998;Nelson, 2009;Basso, 2012;Littler and Littler, 2013). Habitats dominated by RCA are economically and ecologically relevant (Coletti et al., 2017;Tuya et al., 2023) and have high sensitivity to the impacts of ocean warming and acidification (McCoy and Kamenos, 2015;Cornwall et al., 2019;Marchini et al., 2019). ...
... Most members of this polyphyletic grouping belong to one of three main clades: Chlorophyta (green algae), Phaeophyceae (brown algae), and Rhodophyta (red algae). Macroalgae can be found from polar regions to the tropics and range from inhabiting the intertidal zone to nearly 300 m in depth [6,7] in tropical waters (primarily rhodoliths, a group of coralline red algae), although most live in shallower waters of 100 m or less [6]. Macroalgae are all dependent upon specific physical parameters (including light, temperature, salinity, and nutrients) for survival, growth, and reproduction. ...
Marine macroalgae (seaweeds) are important primary global producers, with a wide distribution in oceans around the world from polar to tropical regions. Most of these species are exposed to variable environmental conditions, such as abiotic (e.g., light irradiance, temperature variations, nutrient availability, salinity levels) and biotic factors (e.g., grazing and pathogen exposure). As a result, macroalgae developed numerous important strategies to increase their adaptability, including synthesizing secondary metabolites, which have promising biotechnological applications, such as UV-absorbing Mycosporine-Like Amino Acid (MAAs). MAAs are small, water-soluble, UV-absorbing compounds that are commonly found in many marine organisms and are characterized by promising antioxidative, anti-inflammatory and photoprotective properties. However, the widespread use of MAAs by humans is often restricted by their limited bioavailability, limited success in heterologous expression systems, and low quantities recovered from the natural environment. In contrast, bloom-forming macroalgal species from all three major macroalgal clades (Chlorophyta, Phaeophyceae, and Rhodophyta) occasionally form algal blooms, resulting in a rapid increase in algal abundance and high biomass production. This review focuses on the bloom-forming species capable of producing pharmacologically important compounds, including MAAs, and the application of proteomics in facilitating macroalgal use in overcoming current environmental and biotechnological challenges.
... While δ 13 C values are influenced by environmental conditions such as light, dissolved inorganic carbon (DIC), and nutrients Mackey et al., 2015), the variability in δ 13 C values primarily depend on the taxonomy, morphology, and structural organization of the life forms (Marconi et al., 2011;Velázquez-Ochoa et al., 2022). The CCA are one of the major calcareous macroalgae in the reef ecosystems (Littler and Littler, 2013;Cornwall et al., 2023). The CCA are organisms that cannot move independently in the environment as compared to mobile organisms such as fish and snails, thereby the stable isotope values of the calcified algae could more directly reflect the local or regional water pollution caused by human activities. ...
... Agrupan en la actualidad alrededor de 800 especies, pero se ha estimado que la diversidad de especies es de dos a cuatro veces superior a la actualmente conocida (Richards et al., 2018). En las algas coralinas, el carbonato cálcico les permite construir plantas con segmentos regulares no calcificados (coralinas geniculadas) y otras casi íntegramente calcificadas (coralinas no geniculadas), que varían desde formas diminutas a otras de decenas de centímetros que llegan a formar estructuras sólidas y duraderas que incluso sustentan formaciones como los arrecifes tropicales o los lechos de rodolitos (Woelkerling, 1988;Littler & Littler, 2013;Riosmena et al., 2017). Están distribuidas por todos los mares y en Canarias son un grupo abundante y diverso omnipresente en todas las comunidades bentónicas . ...
La erupción del volcán Tajogaite ha creado un nuevo
ecosistema, un laboratorio natural ideal para el estudio de procesos ecológicos, muchos de los cuales no pueden reproducirse en condiciones controladas de laboratorio. La sucesión primaria se ha podido estudiar de forma temprana, apenas dos meses después del final del proceso eruptivo, y ha incluido diferentes grupos de organismos, lo que nos ha permitido tener una visión amplia de la formación de un ecosistema. Algunos organismos colonizaron las coladas de lava más rápido que otros, la capacidad de movilidad de los peces fue una ventaja que les permitió llegar primero y evolucionar rápidamente hacia comunidades clímax. El resto de comunidades de organismos estudiadas, invertebrados y algas, han evolucionado más lentamente. Sólo en las algas encontramos unreemplazo de especies a través de la sucesión, mientras que en
peces e invertebrados, las especies que colonizaron primero las
coladas de lava fueron esencialmente las mismas que estaban
presentes en la zona de control. Describimos un ecosistema donde
aún las interacciones entre organismos son incipientes, esto ha
dado lugar al asentamiento e insólita proliferación de algunas
especies. Esta contribución, como las futuras en las que estamos
trabajando, nos permitirán aportar conocimiento de las variaciones
espacio-temporales de las comunidades y de las dinámicas a largo
plazo en territorios volcánicos de nueva formación, tan necesarios
para una correcta gestión de la biodiversidad.
... In the Indo-Pacific, the waveward reef crest is composed primarily of certain red algae that lay down thick and dense calcareous sheets and are uniquely resistant to abrasion, breakage, and the crushing forces typical of this zone (Figure 1.9b). These reef-forming agents are referred to as crustose coralline algae (CCA) and their importance in reef construction is well known (Littler and Littler, 2013). Such wave-resistant calcareous structures extend into other shallow-water portions of the rim, including surge channels in the reef flat (Figure 1.8c), and most significantly, below the reef crest as described below. ...
... In the Indo-Pacific, the waveward reef crest is composed primarily of certain red algae that lay down thick and dense calcareous sheets and are uniquely resistant to abrasion, breakage, and the crushing forces typical of this zone (Figure 1.9b). These reef-forming agents are referred to as crustose coralline algae (CCA) and their importance in reef construction is well known (Littler and Littler, 2013). Such wave-resistant calcareous structures extend into other shallow-water portions of the rim, including surge channels in the reef flat (Figure 1.8c), and most significantly, below the reef crest as described below. ...
... Montaggioni (2005) likewise identified coral and skeletal rubble facies as the most prominent features of reef cores in the Indo-Pacific, occupying up to 60% of the total core volume, while Morais et al. (2022) showed that dead If corals do not contribute to reef accretion as much as previously assumed, other organisms may underpin reef accretion. Crustose coralline algae (CCA), for example, have been shown to be key secondary reef builders, able to consolidate and cement reef framework (Littler & Littler, 2013), thus playing an important role in reef accretion (Nash et al., 2013). Kench et al. (2022) showed that vertical reef accretion in the low coral cover wave breaking zone (reef crest) was maintained, even shortly after periods of elevated sea-surface temperatures, by CCA calcification. ...
Aim
The Caribbean and Indo‐Pacific are separate biogeographical realms with distinct biogeographical and evolutionary histories, a 10‐fold difference in biodiversity, and highly disparate sea‐level histories. Since reef morphology often reflects interactions between biological activity and biogeographical history, including sea levels, the widths of shallow coral reef habitats are likely to differ markedly between realms, with ramifications for numerous ecosystem functions. Our goal, therefore, was to assess the impact of global‐scale biogeographical and evolutionary histories on coral reef habitats. Specifically, are Indo‐Pacific reefs wider than their Caribbean counterparts?
Location
Global.
Time Period
Modern.
Major Taxa Studied
Coral reefs.
Methods
We used the Allen Coral Atlas, a global reef mapping system (3 m pixel resolution), to examine 3765 transects, 3 km long and 1 km apart, on 60 reefs across the two realms, quantifying shallow reef habitat widths (Inner and Outer Reef Flat, and Reef Crest) using ArcGIS.
Results
Shallow reef habitat widths were strikingly similar between the Caribbean and Indo‐Pacific. Estimated modal widths diverged by just 37 m; means by just 122 m. Although shallow reef zones appeared to be wider in the Indo‐Pacific, habitat widths on atolls were almost identical across realms (means varying by less than 8 m).
Main Conclusions
Our remote sensing approach provides a global description of the biogeography of coral reefs as biogenic structures. Furthermore, we can assess the relative importance of realm‐wide differences in coral diversity and sea‐level history on reef growth. The striking similarity of reef widths across realms suggests that reef growth (net reef accretion) is largely independent of coral diversity, or sea‐level history, and that other factors may have played a major role in constraining shallow reef widths. These factors may include geomorphology (e.g. antecedent topography and historical accommodation space) and, once at sea level, self‐limiting local hydrodynamics.
... The positive interactions between the two functional guilds promote their coexistence and are key for the functioning of these seaweed forests [5,6]. In the tropics, coralline algae are crucial for the construction of coral reefs, acting as consolidators and binders of the reef framework [7][8][9][10][11]. However, coralline algae not only support coral reefs but also construct extensive reef systems of their own [12][13][14][15]. ...
Ocean warming (OW) and marine heatwaves (MHWs) rapidly transform marine ecosystems, especially when they impact keystone or foundation species. Foundation species such as kelps, fucoids and corals are highly sensitive to heat stress, which threatens the future of temperate seaweed forests and tropical reefs. However, functioning and resilience of these systems also relies on the less conspicuous coralline algae, whose thermal tolerances have gone largely untested. Here, we examined the sensitivity of four temperate coralline algal morphotypes from three different species to four realistic present day and future OW and MHW scenarios (ambient [16°C constant]; ambient+MHW [16°C baseline + a symmetric two-week heatwave with a peak intensity of 18.7°C]; future [18.7°C constant]; future+MHW [18.7°C baseline + a symmetric two-week heatwave with a peak intensity of 21.4°C]). Photo-physiology (e.g., Fv/Fm) and calcification physiology (e.g., proxies for calcifying fluid saturation state ΩCF) were generally unaffected by the treatments, implying a high thermo-tolerance of our study species compared to other important marine foundation species. We ascribe this mainly to their photosynthetic apparatus that, unlike in other photoautotrophs, continued to function under heat stress. Experimental evidence presented here and elsewhere implies that coralline algae are likely to continue to play their crucial ecological roles in a warming ocean. Yet, such predictions are fraught with uncertainty due to the substantial gaps in our knowledge. We attempt to highlight some of these gaps and aim to present potential physiological underpinnings of their thermo-tolerance.
... Without further persisting in terminological issues, bioconstructors are modular and sediment-binding species that modify the physical environment. Hermatypic corals are the most important and best known of reef-building organisms (Scoffin, 1992;Sheppard et al., 2017), but examples may be found also among coralline algae (Chisholm, 2003;Littler and Littler, 2013), bryozoans (Bastos et al., 2018;Cocito et al., 2000), oysters (Grabowski et al., 2012;Lenihan, 1999), vermetid gastropods (Milazzo et al., 2017;Safriel, 1975) and serpulid polychaetes (Bianchi and Morri, 2001;Bosence, 1973). ...
The Serpulidae are a large family of sedentary polychaetes, characterized by a calcareous habitation tube, which they cannot leave. The calcium carbonate tube is in the form of both aragonite and calcite, in fairly constant ratio for each taxon. Tubes are cemented firmly to any hard substrate (in only few species tubes are free). Although in the majority of the species the tubes encrust the substrate for all their length, the distal part may eventually detach and grow erectly. Certain species in dense populations build tubes vertical to the substrate in clumps and cement the tubes to each other. This gives serpulids the capability of forming reef-life structures when densely settling. Despite the relative smallness of the individual tubes (rarely longer than 15 cm and wider than 1 cm), such reef-like structures may cover tens of m², with a layer more than 1 m thick. Serpulid reefs can be divided roughly into seven groups, according to the building modality and the type of habitat they occupy: (i) pseudocolonies; (ii) littoral belts; (iii) subtidal to deep-water reefs; (iv) reefs in coastal lakes and harbours; (v) brackish water reefs; (vi) tapestries in freshwater caves; (vii) biostalactites inside marine caves. The role of serpulid reefs in the ecosystems they inhabit is multifarious and may be distinguished in functions (biomass and production, benthic pelagic coupling, resistance and resilience, reproductive and survivorship strategies, trophodynamics, bioconstruction, living space and refuge, nursery, sediment formation and retention, food for other species, carbonate deposition and storage) and services (water clearance, reef associated fishery, cultural benefits). On the other hand, many serpulids are important constituents of biological fouling, and their calcareous masses damage submerged artefacts, causing huge economic costs. Positive and negative roles of serpulid reefs need to be compared with common metrics; the overall balance, however, is still to be assessed.
... CCA are non-geniculate members of the subclass Corallinophycidae (Class: Florideophyceae, Phylum: Rhodophyta) (Le Gall and Saunders 2007) and are considered less susceptible than other macroalgae to herbivory due to their encrusting nature and low nutritional quality (Montgomery and Gerking 1980;Steneck 1983Steneck , 1985Steneck , 1986Bruggemann et al. 1994;Teichert et al. 2020). CCA are important ecosystem engineers (Nelson 2009;Schubert et al. 2020), contributing calcareous sediment to reefs and stabilizing reef frameworks by binding loose substratum (Littler and Littler 2013;Diaz-Pulido et al. 2014). ...
Niche differentiation is a key stabilizing mechanism in the maintenance of biodiversity and species coexistence. Recent work shows that trophic niche partitioning between parrotfishes (Labridae: Scarini) is more extensive than previously described. One Indo-Pacific species, Scarus spinus , appears highly specialized, scraping crustose coralline algae (CCA) with powerful oral jaws. CCA are of low nutritional value, suggesting that the dietary targets of this parrotfish are protein-rich microphotoautotrophs associated with CCA, particularly filamentous cyanobacteria. We collected feeding substrata samples at mid-shelf and outer-shelf sites near Lizard Island, Great Barrier Reef, Australia, in 2018 and 2019, respectively. Scarus spinus were followed on snorkel. When biting was observed, bite substrata were photographed and then a 22-mm-diameter core extracted around the bite site. Density of biota including filamentous cyanobacteria and diatoms was quantified microscopically on photographs of the bite cores (up to 630 × magnification). The taxonomy of cyanobacteria and CCA was refined using next-generation sequencing of 16S and 18S rRNA genes, respectively. CCA and filamentous cyanobacteria were present on all bite cores and the density of filamentous cyanobacteria where S. spinus fed did not vary between mid-shelf and outer-reef samples. Epiphytic and shallow endophytic cyanobacteria were consistently associated with the CCA where S. spinus fed, including Calothrix spp., Mastigocoleus testarum , Leptolyngbya spp . , Hyella patelloides and Oscillatoriales. Our results emphasize the importance of high-resolution species-specific dietary data for parrotfishes. We conclude that polyphasic methods are essential both for diet tracing and to develop our understanding of the cyanobacteria that are integral to coral reef functioning.
... We expect this bioeroder to be the main responsible for the spongy structure of coralline hills, but confirmation of this hypothesis will need further studies. Also, herbivory over coralline algae can favor the increase in its own structural complexity in a predator-prey profitable interaction, since the constant meristematic removal results in tissue differentiation and redirection growth forming castle-like novel structures (Littler and Littler 2013). ...
algae and rises up from the seamount summit at 60-70 m to 17 m depth. The benthic community is mainly composed by coralline algae and sponges. Fish biomass at Davis coralline hill is dominated by carnivores, mainly top predators such as nurse sharks and large groupers. The relatively shallow reef top presents higher species richness, abundance and distinct trophic structure (mostly omnivore and planktivore species) than the mesophotic zone (with higher abundance of carnivorous fishes). A biogeographic analysis revealed that the reef fish community structure is greatly influenced by a set of dispersal and establishment traits that strongly differs from that encountered on coastal reefs of the central Brazilian coast and on insular reefs of Trindade Island. Gathering information about the ecology and structure of such unique and remote habitat is timely, since the region is under imminent threat such as fishing and mining and lacks international attention.
... However, the 2018 benthic transition from algal turf to CCA dominance at Jarvis marks a positive change. Under the relative dominance model, when both herbivory and nutrient levels are high, CCA is predicted to dominate (Littler and Littler 1984). Similar rapid increases in CCA post-bleaching have been reported in remote reefs in Western Australia (Gilmour et al. 2013), the Phoenix Islands (Obura and Mangubhai 2011) and the Chagos Archipelago (Benkwitt et al. 2019), where the benefits of isolation include high densities of herbivorous fish. ...
Severe thermal stress events occurring on the backdrop of globally warming oceans can result in mass coral mortality. Tracking the ability of a reef community to return to pre-disturbance composition is important to inform the likelihood of recovery or the need for active management to conserve these ecosystems. Here, we quantified annual, temporal changes in the benthic communities for the three years following mass coral mortality at Jarvis Island—an uninhabited island in the Pacific Remote Islands Marine National Monument. While Jarvis experienced catastrophic coral mortality in 2015 due to heat stress resulting from the 2015/16 El Niño, significant annual shifts were documented in the benthic community in the three years post-disturbance. Macroalgal and turf dominance of the benthos was temporary—likely reflecting the high biomass of herbivorous reef fishes post-bleaching—giving way to calcifiers such as crustose coralline algae and Halimeda, which may facilitate rather than impede coral recovery. By 2018, indications of recovery were detectable in the coral community itself as juvenile densities increased and stress-tolerant genera, such as Pavona, exceeded their pre-disturbance densities. However, densities of Montipora and Pocillopora remain low, suggesting recovery will be slow for these formerly dominant taxa. Collectively, the assemblage and taxon-specific shifts observed in the benthic and coral community support cautious optimism for the potential recovery of Jarvis Island’s coral reefs to their pre-disturbance state. Continued monitoring will be essential to assess whether reassembly is achieved before further climate-related disturbance events affect this reef system.
... Sedimentation is one of many potential drivers of contemporary environmental selection. Other biotic factors (e.g., space competitors and grazers) and abiotic factors (e.g., light intensity, nutrient levels, wave intensity, and sand scouring) not examined in this study may also affect the growth (Littler & Littler, 2013;Steneck, 1986) and assembly of CCA (Amado-Filho et al., 2018;Dean et al., 2015;Hind et al., 2019;Sissini et al., 2021). Understanding the effects of these other biotic and abiotic factors -in conjunction to dispersal limitation, sediment tolerance, and substrate preference -on the formation of CCA assemblages is crucial to determine the probably uncommon combination of environmental conditions that permit concretions of CCA in the TAR and other algal reefs. ...
Algal reefs, concreted by crustose coralline algae (CCA), are the main biotic reefs in temperate waters but rare in the subtropics and tropics. The world's largest known intertidal algal reef in the subtropics is the Taoyuan Algal Reef (TAR) located in the northwestern coast of Taiwan. The biodiversity and ecology of the TAR are scarcely explored, and now the reef is imperiled by industrialization. Here, we document cryptic species of CCA in Taiwan, particularly the TAR, by sequencing the psbA genes of over 1800 specimens collected across Taiwan. We also examine the ecological background of the TAR by surveying its benthic composition and measuring its environmental parameters. Our data reveal that the TAR harbours a high diversity of cryptic CCA species (27 molecular operational taxonomic units, or mOTUs), many of which are potentially new to science (18 mOTUs) and/or endemic to the TAR (9 mOTUs). Comparing the CCA species inventory of the TAR with the rest of Taiwan shows that the TAR represents a unique hotspot of CCA taxa in the waters of Taiwan. Our analyses show that variation in the CCA assemblages in the TAR is associated with geographic distance, sedimentation, and substrate type (for example, reef vs. hermit crab shell), suggesting that dispersal limitation and contemporary environmental selection shape the CCA assemblages in the TAR. The data from this study can inform the monitoring of human impacts on the health of the TAR and contribute to our understanding of the ecological processes underlying algal reef development.
... Despite having lower calcification rates than the massive corals, A. cervicornis provides a unique habitat for the biodiversity of species which reside in the dense thickets formed by this branching coral (Tunnicliffe 1981;Precht et al. 2002). The lowest metabolic rates were recorded for crustose coralline algae; biogenic calcifiers which reinforce and strengthen the calcium carbonate matrix to cover otherwise exposed coral skeleton (Littler and Littler 2013). In addition, they promote calcification by scleractinian corals (Chisholm 2000) via inducing larval settlement and providing substrate for juvenile corals to grow (Heyward and Negri 1999). ...
Coral reef metabolism underpins ecosystem function and is defined by the processes of photosynthesis, respiration, calcification, and calcium carbonate dissolution. However, the relationships between these physiological processes at the organismal level and their interactions with light remain unclear. We examined metabolic rates across a range of photosynthesising calcifiers in the Caribbean: the scleractinian corals Acropora cervicornis, Orbicella faveolata, Porites astreoides, and Siderastrea siderea, and crustose coralline algae (CCA) under varying natural light conditions. Net photosynthesis and calcification showed a parabolic response to light across all species, with differences among massive corals, branching corals, and CCA that reflect their relative functional roles on the reef. At night, all organisms were net respiring, and most were net calcifying, although some incubations demonstrated instances of net calcium carbonate (CaCO3) dissolution. Peak metabolic rates at light-saturation (maximum photosynthesis and calcification) and average dark rates (respiration and dark calcification) were positively correlated across species. Interspecies relationships among photosynthesis, respiration, and calcification indicate that calcification rates are linked to energy production at the organismal level in calcifying reef organisms. The species-specific ratios of net calcification to photosynthesis varied with light over a diurnal cycle. The dynamic nature of calcification/photosynthesis ratios over a diurnal cycle questions the use of this metric as an indicator for reef function and health at the ecosystem scale unless temporal variability is accounted for, and a new metric is proposed. The complex light-driven dynamics of metabolic processes in coral reef organisms indicate that a more comprehensive understanding of reef metabolism is needed for predicting the future impacts of global change.
... Studies regarding the influence of thermally fluctuating environments on the response to temperature rise in coralline algae, a group of benthic organisms that has been shown to experience often negative impacts related to seawater temperature increase (Martin and Hall-Spencer, 2017;Cornwall et al., 2019), and their potential capacity for thermal priming are currently missing. These algae fulfill crucial ecological roles throughout the oceans, such as building extensive, worldwide distributed coastal ecosystems, the rhodolith beds (Foster, 2001;Riosmena-Rodríguez et al., 2017), or cementing and providing substrate for invertebrate larval settlement in coral reefs (e.g., Adey, 1978;Steneck, 1986;Littler and Littler, 2013). Though, in contrast to other ecosystems (e.g., coral reefs, kelp forests) still little information is available regarding their response to increased seawater temperature. ...
Recently, increased attention is being paid to the importance of environmental history in species’ responses to climate-change related stressors, as more variable and heterogeneous environments are expected to select for higher levels of plasticity in species tolerance traits, compared to stable conditions. For example, organisms inhabiting environments with highly fluctuating thermal regimes might be less susceptible to the increasing frequency and intensity of marine heatwaves (MHWs). In this study, we assessed the metabolic and calcification responses of the rhodolith-bed forming Phymatolithon lusitanicum, from a coastal region that is strongly influenced by frequent changes between upwelling and downwelling conditions, to a simulated MHW scenario, with and without prior exposure to a moderate thermal stress. This allowed determining not only the influence of the species’ long-term thermal history on its resilience against MHWs, but also the rhodoliths capacity for short-term thermal stress memory and its importance during posterior MHW-exposure. Our findings indicate that the rhodoliths experienced negative impacts on daily net primary production (DNP) and calcification (DNC) during the MHW. The effect on the former was only temporary at the beginning of the MHW, while DNC was highly impacted, but exhibited a quick recovery after the event, suggesting a high resilience of the species. Furthermore, prior exposure to a moderate temperature increase, such as those occurring frequently in the natural habitat of the species, mitigated the effects of a subsequent MHW on DNP, while promoting a faster recovery of DNC after the event. Thus, our findings (1) support the hypothesis that benthic organisms living in nearshore habitats may benefit from the natural short-term temperature fluctuations in these environments with an increased resistance to MHW impacts and (2) provide first-time evidence for thermally induced stress memory in coralline algae.
... The algal reef ecosystem is one of the rarest ecosystems in the world . Algal reefs are constructed mainly of crustose coralline algae (CCA), unlike coral reefs, in which CCA is less prevalent and its calcareous deposit can cement corals and debris together (Wray 1998;Littler and Littler 2013). Algal reefs form in layers, and this creates numerous pores and crevices that provide many microhabitat types and lead to high biodiversity (Yu et al. 2020). ...
Algal reefs are one of the world's rare and poorly understood ecosystems. They are mainly distributed in the Mediterranean Sea, but one notable exception-an intertidal algal reef ecosystem in northwestern Taiwan-stretches for 27 km along the coast of Taoyuan, making it probably the largest algal reef coast found in shallow water. Despite the reef's rarity and striking characteristics, the coastal land that it is part of has undergone a series of developments and is now surrounded by industrial parks. Brachyuran crabs are one of the most abundant and visible groups of organisms in the intertidal zone. In the present study, we investigated the brachyuran crab community in this reef to provide a more detailed record of brachyuran crab species compositions in this intertidal algal reef ecosystem and illustrate the characteristics of this understudied ecosystem by comparing its species diversity and abundance with three natural variables-sampling time, tidal level, and season-in a wildlife refuge and north of the refuge. Two methods were used in the study: a qualitative method (to determine the species richness) and a quantitative method (to estimate the population density). We identified a total of 52 brachyuran species from 13 families in the habitats. The highest species richness was found in Datan G2, north of the wildlife refuge. The crab species composition in this algal reef is different from its compositions in coral and rocky reefs. Our analysis indicated that the species abundance is affected by multiple factors, and a single investigation is not enough to reflect the true population density of brachyuran crabs on this reef. In addition, we found that the sites outside the wildlife refuge were in much better condition than those in the wildlife refuge, and should therefore be included in the wildlife refuge. In particular, Datan, located north of the wildlife refuge, had the highest species richness, and the area's species composition was different from that of the nearby wildlife refuge. Thus, we strongly recommend that a) the Datan area be protected to maintain this high crab diversity and b) further research be performed to better understand brachyuran crab biology in the intertidal algal reef ecosystem. Citation: Li KC, Liu HC, Lin HC. 2021. Multiple environmental factors increase the niche complexity and species diversity of brachyuran crabs in an intertidal algal reef ecosystem in northwestern Taiwan. Zool Stud 60:73.
... Cover of CCA in this study was found to dominate the artificial reef. Research on the distribution of CCA reveals that they tend to dominate areas where corals are inhibited by strong wave action (Littler and Littler, 2013). The artificial reef in this study, was located in shallow subtidal water (<2 m depth) and close to the shore (<35 m distance), where wave action was strong. ...
A R T I C L E I N F O Keywords: 18th century Artificial reef Crustose coralline algae Turf algae Palythoa caribaeorum Millepora spp. A B S T R A C T With increasing maritime activities in the proximity of coral reefs, a growing number of manmade structures are becoming available for coral colonisation. Yet, little is known about the sessile community composition of such artificial reefs in comparison with that of natural coral reefs. Here, we compared the diversity of corals and their competitors for substrate space between a centuries-old manmade structure and the nearest natural reef at St. Eustatius, eastern Caribbean. The artificial reef had a significantly lower species richness and fewer competitive interactions than the natural reef. The artificial reef was dominated by a cover of crustose coralline algae and zoantharians, instead of turf algae and fire corals on the natural reef. Significant differences in species composition were also found between exposed and sheltered sites on both reefs. Our study indicates that even a centuries-old manmade reef cannot serve as a surrogate for natural reefs.
... CCA is an important component in reef habitats, helping to maintain reef complexity and reducing erosion from strong wave energy (Tâmega and Figueiredo, 2019). The ability of CCA to stabilize reef structure makes communities with high CCA cover more resistant to disturbances such as typhoons and waves that cause mechanical damage (Littler, 1972;Littler and Littler, 2013). In the future, those characteristics may further emphasize the expansion of communities structured around CCA (Cornwall et al., 2019). ...
Differences in the initial configuration of ecological communities may lead to contrasting trajectories when facing environmental changes. Here, we propose to uncover the determinism of benthic communities by carrying out a detailed investigation of their response to small-scale modification of environmental conditions, including physical, chemical, and geological factors. At ten locations (confounding site and depth) in Northern Taiwan, communities were delineated using a morpho-functional classification of the organisms. A k-means clustering was used to identify k homogenous groups among transects Their environmental determinism was examined by combining this result with 16 environmental variables of transect conditions into a regression tree framework. Biotic and abiotic data were further analyzed with a Multivariate Regression Tree (MRT) to ascertain the hierarchical environmental determinism. The classifications produced by both approaches were compared using the Adjusted Rand index (ARI) to assess the predictive power of unsupervised clustering on its missing explanatory components (abiotic variables). k-means and MRT produced five clusters, respectively, with a similarity of 0.82 in ARI. Wave motion, followed by substrate types resolved most of the variance, while chemical factors in this study were uniform throughout the region. Comparable structures for both methods demonstrated that the delineated clusters matched with contrasting environmental conditions (clustering groups) which could be explained by the existence of various benthic communities. Further consideration of these different communities and their environmental context will be important in determining their trajectories under global changes and may help in the interpretation of community modifications with changing environmental conditions.
... This extreme position on the PC2trait axis was echoed in the feeding axis, PC1bitecore, because S. psittacus and S. schlegeli targeted substrata with high bioerosion, the tallest turf and without CCA. These substrata were crumbly in nature owing to high bioerosion and a lack of stabilization that would typically arise through the binding action of CCA (Fabricius & De'Ath, 2001;Littler & Littler, 2013b). The feeding substrata targeted by these two Scarus species were loose and coarse, suggesting that relatively little bite force is necessary to harvest their diet. ...
Adaptive diversification is a product of both phylogenetic constraint and ecological opportunity. The species-rich parrotfish genera Scarus and Chlorurus display considerable variation in trophic cranial morphology, but these parrotfishes are often described as generalist herbivores. Recent work has suggested that parrotfish partition trophic resources at very fine spatial scales, raising the question of whether interspecific differences in cranial morphology reflect trophic partitioning. We tested this hypothesis by comparing targeted feeding substrata with a previously published dataset of nine cranial morphological traits. We sampled feeding substrata of 15 parrotfish species at Lizard Island, Great Barrier Reef, Australia, by following individuals until focused biting was observed, then extracting a bite core 22 mm in diameter. Three indices were parameterized for each bite core: substratum taphonomy, maximum turf height and cover of crustose coralline algae. Parrotfish species were spread along a single axis of variation in feeding substrata: successional status of the substratum taphonomy and epilithic and endolithic biota. This axis of trophic variation was significantly correlated with cranial morphology, indicating that morphological disparity within this clade is associated with interspecific partitioning of feeding substrata. Phylogenetic signal and phylomorphospace analyses revealed that the evolution of this clade involved a hitherto-unrecognized level of trophic diversification.
... We conclude this because the environmental tolerances of CCA in terms of sea level fluctuation are much wider than those of reef corals. Most CCA species appear uniquely tolerant of aerial exposure 10 . Additionally, many CCA are very well adapted to changes in salinity and especially to low photon irradiances 30 . ...
Crustose coralline red algae (CCA) play a key role in the consolidation of many modern tropical coral reefs. It is unclear, however, if their function as reef consolidators was equally pronounced in the geological past. Using a comprehensive database on ancient reefs, we show a strong correlation between the presence of CCA and the formation of true coral reefs throughout the last 150 Ma. We investigated if repeated breakdowns in the potential capacity of CCA to spur reef development were associated with sea level, ocean temperature, CO2 concentration, CCA species diversity, and/or the evolution of major herbivore groups. Model results show that the correlation between the occurrence of CCA and the development of true coral reefs increased with CCA diversity and cooler ocean temperatures while the diversification of herbivores had a transient negative effect. The evolution of novel herbivore groups compromised the interaction between CCA and true reef growth at least three times in the investigated time interval. These crises have been overcome by morphological adaptations of CCA.
Successful larval recruitment is essential to the growth of coral reefs and therefore plays a key role in the recovery of degraded reefs worldwide. The rising intensity and frequency of environmental disturbance events and their effect on the establishment of new corals is outpacing the natural capacity of coral reefs to recover. To counter this, restoration programmes are increasingly turning to interventionist approaches to enhance coral recruitment, including mass-breeding corals in aquaria for subsequent deployment in the field. Coral sexual propagation has the potential to generate large numbers of genetically diverse coral recruits, but widespread application is still limited by the ability to reliably guarantee the successful settlement of coral larvae. Identifying the origins of biochemical cues that enhance coral settlement is a prerequisite to improving coral larval settlement on key locations and substrates. Microbial biofilms and microbes associated with crustose coralline algae have been shown to induce coral larval settlement, yet the specific taxa and mechanisms involved are poorly understood. In this review we synthes current literature on microbial settlement cues and the challenges associated with untaizengling the origin of individual cues originating within complex microbial communities. Furthermore, we call attention to the importance of interrogating microbial interactions with a holistic community approach to further our knowledge of both coral larval settlement inducers and inhibitors. Obtaining a better understanding of microbial interactions associated with coral settlement will lead to more effective approaches to restoration, from engineering inductive microbial communities to synthesising biochemical cues that can support coral larval settlement for aquaculture and reef recovery.
Analyzing the environmental factors affecting benthic communities in coastal areas is crucial for uncovering key factors that require conservation action. Here, we collected benthic and environmental (physical-chemical-historical and land-based) data for 433 transects in Taiwan. Using a k-means approach, five communities dominated by crustose coralline algae, turfs, stony corals, digitate, or bushy octocorals were first delineated. Conditional random forest models then identified physical, chemical, and land-based factors (e.g., light intensity, nitrite, and population density) relevant to community delineation and occurrence. Historical factors, including typhoons and temperature anomalies, had only little effect. The prevalent turf community correlated positively with chemical and land-based drivers, which suggests that anthropogenic impacts are causing a benthic homogenization. This mechanism may mask the effects of climate disturbances and regional differentiation of benthic assemblages. Consequently, management of nutrient enrichment and terrestrial runoff is urgently needed to improve community resilience in Taiwan amidst increasing challenges of climate change.
Crustose coralline algae (CCA) are important ecosystem engineers and carbonate producers today and in the geological past. While there is an increasing number of publications on CCA every year, it is evident that there are many misunderstandings and inconsistencies in the assignment of CCA to taxonomic and functional groups. This is partly because CCA are treated by biologists, ecologists and palaeontologists as well as covered by studies published in journals ranging from geo- to biosciences, so that there is often a mixture of terminology used and differing scientific focus. In this review, a comprehensive overview is given on what is known about CCA, their functional traits and their roles in environments from the present and the past. In this context, some bridges are built between the commonly different viewpoints of ecologists and palaeontologists, including suggesting a common and straightforward terminology, highlighting and partially merging different taxonomic viewpoints as well as summarizing the most important functional traits of CCA. Ideally, future studies should seek to quantitatively analyse potential implications for CCA and their associated organisms under ongoing global change.
Crustose coralline algae (CCA) play a key role in invertebrate recruitment, yet their influence on the settlement of patellid
limpets is under discussion. This study is aimed at resolving the role of CCA as a settlement inducer for patellid limpets,
providing insight into the influence of different CCA-related factors. The larvae of the economically valuable limpet Patella
candei were used as a model. Six assays were performed: (1) different CCA assemblages, (2) exposure time, (3) artificial
removal of epibionts, (4) substrate area, (5) soluble cues (CCA-conditioned seawater), and (6) substrate selection in a choice
experiment. Settlers were identified by velum loss and teleoconch development. Species composition of the CCA assem-
blages significantly influenced settlement, with a preference for Titanoderma pustulatum and combined Neogoniolithon sp.
and Hydrolithon farinosum crusts. The substrates dominated by Agissea inamoena, marginal presence of CCA or which
epibionts were artificially removed, were statistically similar to those in the negative control. The ratio of settlers increased
until 4 days of exposure, after which it remained stable over time. The results support that CCA releases soluble cues with
settlement-inducing effect on P. candei larvae, explaining why the ratio of settlers increased with substrate area. The choice
experiment suggests that P. candei larvae have limited selectivity with respect to the substrate surface. In conclusion, the
present study points to the relevance of CCA assemblages as settlement substrates for limpet larvae, with an impact on limpet
recruitment in the wild as well as on the production of post-larvae for limpet aquaculture.
CaCO3 precipitates occur inside a few cyanobacteria and green algae. More common is precipitation on the surface of cyanobacteria, a range of algae and aquatic plants, and in invaginations of the cell wall in terrestrial plants (cystoliths). In coccolithophores and calcified dinoflagellates, CaCO3 is precipitated with organic matter in intracellular vesicles and the resulting structures are externalised. The precipitation of CaCO3 on the surface of photosynthesising structures is related to the consumption of CO2 in photosynthesis. CO2 production by root respiration can solubilise soil CaCO3. A few cyanobacteria and eukaryotic algae can bore through solid CaCO3 by removing Ca2+ and adding H+ at the site of boring, generating soluble inorganic C that can be used in photosynthesis. Ca(COO)2 is precipitated in the vacuoles of many algae and plants, and the cell walls of some plants.An outcome of precipitation of CaCO3 using CO3= produced from CO2, and Ca2+, is the production of H+; the same is the case for precipitation of Ca(COO)2 from (COOH)2 and Ca2+. The H+ produced by Ca(COO2) can be used to neutralise OH− produced in NO3− assimilation in the shoot without increasing cell osmolarity. There is no evidence of CaCO3 fulfilling this role. Another outcome of CaCO3 and Ca(COO)2 precipitation is Ca2+ immobilisation, though with little evidence of remobilisation of Ca2+ under Ca2+ deficiency. Other consequences of CaCO3 and Ca(COO)2 precipitation are light scattering and increased density, and ‘alarm photosynthesis’. Defence against herbivores and pathogens is better established for Ca(COO)2 than for CaCO3, and pollen release from anthers is a function of Ca(COO)2 but not CaCO3.KeywordsAcid-base regulationAlarm photosynthesisCalciumCarbonateInteractions with photonsOxalate
Pada tahun 2020, satu ekspedisi saintifik telah dilaksanakan di perairan Perak oleh para penyelidik Pusat Penyelidikan Taman Laut Negara dengan kerjasama Universiti Kebangsaan Malaysia, Selangor. Ia bertujuan bagi mengenal pasti potensi perairan Kepulauan Sembilan untuk dijadikan sebagai salah satu bentuk kawasan erlindungan seperti Taman Laut atau Taman Negeri. Kepulauan tersebut meliputi sembilan buah
pulau iaitu Pulau Agas, Pulau Batu Hitam, Pulau Batu Putih, Pulau Buluh, Pulau alang, Pulau Nipis, Pulau Payong, Pulau Rumbia dan Pulau Saga
Protecting the environment and the benefits it provides is essential. This emphasizes the need to identify, conserve, and manage essential ecosystem service supply regions in order to sustain biodiversity and ecosystem services. Information on ecosystem services at each priority location is therefore necessary to help in conveying the value of nature to decision makers at all levels in order to encourage the establishment of development policies that are in accordance with biodiversity protection, which would subsequently have an influence on the supply of ecosystem services. A number of methodologies, models, and instruments for measuring ecosystem services at the local, regional, and global levels have been developed for this purpose, one of which is The Ecosystem Services of Site-based Assessment (TESSA).
Located on the northern coast of Santa Maria Island (Azores Archipelago, central North Atlantic), the Lagoinhas section preserves a carbonate buildup correlated with Marine Isotope Substage (MIS) 5e, the warmest interval of the Last Interglacial. The buildup is formed mainly by crustose coralline algae (CCA) identified as Spongites sp., and some subordinate crusts of Lithophyllum sp. and Neogoniolithon sp., as well as cf. Titanoderma sp.. Extant CCA buildups are not recorded in the archipelago. Herein, we describe in detail the morphological and taphonomical features of the Lagoinhas CCA buildup and interpret the environment in which it grew. Additionally, this buildup is compared with another of similar age, exposed in the Prainha-Praia do Calhau section on the island's opposite southern coast. The hydrodynamic regime appears to play a crucial role in the development of Azorean CCA buildups during the MIS 5e.
Calcareous macroalgae are of particular ecological importance as primary producers, carbonate sediment builders, and habitat providers in coral reef ecosystems. Ocean warming is a major threat to calcareous algae, but it remains unclear exactly how these algae will respond to it. In this study, the potential physiological impacts of ocean warming on calcareous alga Amphiroa fragilissima were evaluated in laboratory experiments. Increasing temperature from 26 to 28°C had positive effects on algal growth rate and chlorophyll a content, but these parameters decreased significantly at 32°C, which is 5°C above the annual mean temperature in the study region. Algal bleaching occurred at 34°C. There were no significant differences in CaCO3 content of thalli among different temperatures; however, calcification rate was inhibited significantly at 32 and 34°C. Transcriptome analyses using the Illumina RNA‐seq platform showed that differentially expressed genes were annotated mainly in the categories of steroid biosynthesis, gap junction, ribosome and mTOR signaling pathway. The expression levels of PsbA and PsbP were suppressed at 32°C, implying that inactivation of photosystem II could be a main reason for the decreased photosynthetic rate. Down‐regulation of the genes encoding carbonic anhydrase and nitrate reductase was observed at 32°C, which could inhibit growth rate. Additionally, several genes that might be related to calcification were identified, including CAMK, CDPK and CAM and genes encoding alpha‐catenin and carbonic anhydrase. This study contribute to our understanding of the effects of temperature on algal calcification and provide a theoretical basis to protect ecological diversity of coral reef ecosystems.
Durante dos expediciones al Pacífico norte chocoano en agosto de 2015 y abril de 2016 se estudiaron las algas asociadas a los riscales y morros. Se identificaron 59 especies de algas, entre Rhodophyta (39), Ochrophyta- Phaeophyceae (10), Chlorophyta (6) y Cyanobacteria (4). Como resultado del proyecto cuatro especies se reportaron por primera vez para el Pacífico Oriental Tropical, 20 más son primer registro para Colombia y seis son nuevos reportes para el Pacífico colombiano. Los nuevos reportes representan el 52% del total de especies registradas; el 48% restante habían sido reportadas en la isla Gorgona, el sector de Tumaco y algunas localidades del PNCh, principalmente en Bahía Solano.
Nitrogen (N) is a limiting nutrient in highly productive tropical coral reefs, despite its key role for primary production. This requires efficient (re)cycling of N by the dwelling organisms, including the key reef ecosystem engineers, the hard corals. As such, corals evolved symbiotic relationships with eukaryotic and prokaryotic microbes, together called a holobiont, which aid in nutrient acquisition and recycling. The nutrient exchange symbiosis between the coral host and the eukaryotic photosynthetic dinoflagellates of the family Symbiodiniaceae has given corals an ecological advantage over other functional groups such as algae. The Symbiodiniaceae provide the coral host with carbon (C) rich photosynthates, while in return, the Symbiodiniaceae receive N and phosphorus (P). Additionally, diazotrophs, microbes capable of fixing atmospheric dinitrogen (N2), can provide the coral holobiont with bioavailable N. Coral holobionts benefit from low internal availability of N as N-limitation may maintain steady translocation of the photosynthates on which the corals rely. Thus, coral holobionts may be particularly susceptible to increases in (environmental) dissolved inorganic N (DIN) due to e.g. anthropogenic input, or stimulated activity of diazotrophs. As such, corals likely have mechanisms in place for the alleviation of excess N, i.e. denitrification, which may ultimately aid coral functioning.
This thesis aims at extending the current knowledge on biogeochemical cycling of N associated with coral holobionts. Specifically, in addition to N2 fixation, we tested whether the antagonistic N-cycling pathway to N2 fixation, i.e. denitrification, is an active pathway in coral holobionts and whether it is affected by environmental change. In addition, we measured N-cycling pathways associated with other coral reef organisms and substrates under environmental change. This allowed us to make inferences for coral reef functioning when exposed to global and local stressors. We applied a combination of physiological and molecular analyses and used the strong seasonality of the northern and central Red Sea as a natural laboratory.
Our findings reveal that denitrification was actively associated with all investigated coral species. Similar to diazotrophy, denitrification may thus be ubiquitously associated with coral holobionts. Under stable environmental conditions, denitrification and N2 fixation aligned and both N-cycling pathways correlated with Symbiodiniaceae cell densities. Thus, the relationship between denitrification and N2 fixation may be the result of a shared organic C limitation (by translocated photosynthates from the Symbiodiniaceae) within the holobiont. Higher seasonal availability of DIN (leading to higher DIN:dissolved inorganic P [DIP] ratios) dynamically shifted the ratio of denitrifiers and diazotrophs, in favour of the denitrifiers. The proliferation of Symbiodiniaceae suggests incomplete alleviation of excess N by denitrification. Indeed, Symbiodiniaceae cell densities also correlated with environmental DIN availability. In response to moderate in situ eutrophication of DIN and DIP, both N-cycling pathways more than doubled in activity. Surprisingly, the Symbiodiniaceae populations remained stable. In addition, there was no significant incorporation of N originating from the eutrophication event in the Symbiodiniaceae. This suggests that N-limitation was maintained, likely assisted by denitrification. These findings suggest that the dynamic interplay of denitrification and N2 fixation may regulate Symbiodiniaceae populations, but the extent to which they maintain N-limitation may depend on the environmental availability of DIN and DIP.
By comparing coral holobiont associated N-cycling to other functional groups on coral reefs, we postulate that under local and global stress scenarios, coral holobionts may lose the competition for space to algae as they 1) can strongly capitalize on (anthropogenic) nutrient inputs, 2) have high associated N2 fixation
VI
rates that increase in response to ocean warming and moderate N/P eutrophication, and/or 3) have low associated denitrification. Turf algae and coral rubble exhibited ∼100-fold higher N2 fixation rates compared to hard corals. Contrastingly, denitrification rates were as low as those associated with hard corals. Therefore, coral reefs in the process of shifting towards algae dominance may get caught in a positive feedback loop where dead coral (coral rubble) is rapidly overgrown by algae which in return naturally provide the reef with bioavailable N. This may facilitate higher growth rates of reef algae.
Collectively, the results described in this thesis suggest that the interplay of N2 fixation and denitrification associated with coral holobionts may indeed aid in coral functioning by maintaining healthy populations of Symbiodiniaceae. Increased activity of diazotrophs induced by thermal stress, both associated with the coral holobiont and other dwelling organisms, as well as eutrophication of N may ultimately shift the coral holobionts’ internal N:P ratios towards P limitation as denitrifiers may be unable to alleviate excess N. Thus, future management efforts should focus strongly on the local prevention of N eutrophication and the mitigation of global warming.
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