Living evidence of a fossil survival strategy raises hope for warming-affected corals

Climate change is affecting reef-building corals worldwide, with little hope for recovery. However, coral fossils hint at the existence of environmental stress–triggered survival strategies unreported in extant colonial corals. We document the living evidence and long-term ecological role of such a survival strategy in which isolated polyps from coral colonies affected by warming adopt a transitory resistance phase, in turn expressing a high recovery capacity in dead colony areas. Such processes have been described in fossil corals as rejuvenescence but were previously unknown in extant reef-builder corals. Our results based on 16 years of monitoring show the significance of this process for unexpected recoveries of coral colonies severely affected by warming. These findings provide a link between rejuvenescence in fossil and extant corals and reveal that beyond adaptation and acclimatization processes, modern scleractinian corals show yet undiscovered and highly effective survival strategies that help them withstand and recover from rapid environmental changes

Is the local extinction of Pinna nobilis facilitating Pinna rudis recruitment?

Until the late 2010s the spiny fan-mussel Pinna rudis shared habitat in many Mediterranean sites with Mediterranean endemic Pinna nobilis, which dominated in abundance but that has gone locally extinct in most of its distribution area due to a recent widespread disease outbreak. In the Columbretes Islands Marine Reserve (NW Mediterranean) both species coexisted until 2017, when P. nobilis populations completely disappeared. In spring 2021 we revisited 7 permanent plots covering 1,485 m2 that had been previously monitored during the period from 2005 to 2009. We found that although previous studies described P. rudis populations as stable with low recruitment rates, recruitment after 2017 increased in comparison to 2005-2009. At least two cohorts of recruits (~3 and ~1 year in age) were to be found both within the plots as well as in other areas throughout the Columbretes archipelago, colonizing areas previously occupied by P. nobilis. We hypothesize that P. rudis has been benefited by the local extinction of the sibling species P. nobilis, most probably as a result of reduced interspecific competition. The ecological role once played mainly by P. nobilis as the dominant species, might now be taken over by P. rudis, whose populations could grow during the oncoming years

Biogeographic Differences in the Microbiome and Pathobiome of the Coral Cladocora caespitosa in the Western Mediterranean Sea.

The endemic Mediterranean zooxanthellate scleractinian reef-builder Cladocora caespitosa is among the organisms most affected by warming-related mass mortality events in the Mediterranean Sea. Corals are known to contain a diverse microbiota that plays a key role in their physiology and health. Here we report the first study that examines the microbiome and pathobiome associated with C. caespitosa in three different Mediterranean locations (i.e., Genova, Columbretes Islands, and Tabarca Island). The microbial communities associated with this species showed biogeographical differences, but shared a common core microbiome that probably plays a key role in the coral holobiont. The putatively pathogenic microbial assemblage (i.e., pathobiome) of C. caespitosa also seemed to depend on geographic location and the human footprint. In locations near the coast and with higher human influence, the pathobiome was entirely constituted by Vibrio species, including the well-known coral pathogens Vibrio coralliilyticus and V. mediterranei. However, in the Columbretes Islands, located off the coast and the most pristine of the analyzed locations, no changes among microbial communities associated to healthy and necrosed samples were detected. Hence, our results provide new insights into the microbiome of the temperate corals and its role in coral health status, highlighting its dependence on the local environmental conditions and the human footprint

Long-term responses of the endemic reef-builder Cladocora caespitosa to Mediterranean warming

Recurrent climate-induced mass-mortalities have been recorded in the Mediterranean Sea over the past 15 years. Cladocora caespitosa, the sole zooxanthellate scleractinian reef-builder in the Mediterranean, is among the organisms affected by these episodes. Extensive bioconstructions of this endemic coral are very rare at the present time and are threatened by several stressors. In this study, we assessed the long-term response of this temperate coral to warming sea-water in the Columbretes Islands (NW Mediterranean) and described, for the first time, the relationship between recurrent mortality events and local sea surface temperature (SST) regimes in the Mediterranean Sea. A water temperature series spanning more than 20 years showed a summer warming trend of 0.06°C per year and an increased frequency of positive thermal anomalies. Mortality resulted from tissue necrosis without massive zooxanthellae loss and during the 11-year study, necrosis was recorded during nine summers separated into two mortality periods (2003-2006 and 2008-2012). The highest necrosis rates were registered during the first mortality period, after the exceptionally hot summer of 2003. Although necrosis and temperature were significantly associated, the variability in necrosis rates during summers with similar thermal anomalies pointed to other acting factors. In this sense, our results showed that these differences were more closely related to the interannual temperature context and delayed thermal stress after extreme summers, rather than to acclimatisation and adaption processes

Ulovi manjića morskog, Molva molva (Linnaeus, 1758) se i dalje događaju u sjeverozapadnom dijelu Sredozemnog mora

The ling Molva molva is a widespread gadid in the Northeast Atlantic and one example of a poorly studied species of particular interest, being its distribution affected by climate warming. The ling supposedly occurs in the cold waters of the Northwestern Mediterranean Sea, where it used to be commonly fished, but to our best knowledge, records of M. molva after the 1990s are not available from the scientific literature. Here we report the recent capture of two individuals, one of them of considerable size, at 35 nautical miles off the coast of Castelló (Spain, NW Mediterranean).Manjić morski (Molva molva) je široko rasprostranjena vrsta u sjeveroistočnom Atlantiku i jedan od primjera slabo istraženih vrsta od posebnog interesa zbog njegove rasprostranjenosti koja je pod utjecajem zagrijavanja klime.Manjić morski se navodno pojavljuje u hladnim vodama sjeverozapadnog Sredozemnog mora, gdje je nekad bio uobičajeni ulov, ali prema našim saznanjima, zapisi o Molva molva nakon 1990-ih nisu dostupni iz znanstvene literature. U ovom radu navodimo nedavni ulov dvije jedinke, od kojih je jedna znatne veličine, na 35 nau-tičkih milja od obale Castelló (Španjolska)

Coexistencia del coral formador de arrecifes Cladocora caespitosa y la macroalga formadora de dosel Treptacantha ballesterosii: descripción de un nuevo hábitat mediterráneo

Shallow Mediterranean rocky environments are usually dominated by macroalgae, but the stony colonial zooxan­thellate coral Cladocora caespitosa is able to build extensive banks in some particular areas. Although zooxanthellate corals and benthic macroalgae are expected to compete for light and space when overlapping in the same habitat, there is previous evidence that C. Caespitosa and Mediterranean macroalgae do not suffer from competitive exclusion when living together. Here we characterize a new and unique Mediterranean habitat where the reef-building coral C. Caespitosa and erect seaweeds of the order Fucales (Cystoseira s.l.) coexist. In this new habitat C. Caespitosa reaches 34% cover and densities of Cystoseira s.l. (mainly Treptacantha ballesterosii) are much higher than values reported from other sites. Interestingly, abundances of T. Ballesterosii and C. Caespitosa show a positive relationship, suggesting that some kind of facilitation mechanism is taking place. These findings challenge the theory of competitive exclusion between corals and macroalgae and launch a wide array of possible open discussions on coral-macroalgae interactions.Los ambientes rocosos someros del Mediterráneo están habitualmente dominados por macroalgas, no obstante, el coral colonial zooxantelado Cladocora caespitosa es capaz de formar bancos extensos en algunos lugares. Aunque es prede­cible que los corales con zooxantelas y las algas bentónicas compitan por la luz y el espacio cuando coinciden en el mismo hábitat, hay evidencias previas de que C. Caespitosa y las algas mediterráneas no se excluyen competitivamente cuando viven juntas. En este trabajo se caracteriza un nuevo y único hábitat mediterráneo donde el coral formador de arrecifes C. caespi­tosa y algas erectas del orden Fucales (Cystoseira s.l.) coexisten. En este hábitat nuevo C. Caespitosa alcanza coberturas del 34% y las densidades de Cystoseira s.l. (principalmente de Treptacantha ballesterosii) son mucho mayores que los valores encontrados en otros lugares. Remarcablemente, las abundancias de T. Ballesterosii y C. Caespitosa muestran una relación positiva, sugiriendo que existe algún tipo de mecanismo de facilitación. Este hallazgo pone en jaque la teoría de exclusión competitiva entre corales y macroalgas, a la vez que puede iniciar un amplio abanico de discusiones en las interacciones entre corales y macroalgas

Experimental evidence of synergistic effects of warming and invasive algae on a temperate reef-builder coral

In the current global climate change scenario, stressors overlap in space and time, and knowledge on the effects of their interaction is highly needed to understand and predict the response and resilience of organisms. Corals, among many other benthic organisms, are affected by an increasing number of global change-related stressors including warming and invasive species. In this study, the cumulative effects between warming and invasive algae were experimentally assessed on the temperate reef-builder coral Cladocora caespitosa. We first investigated the potential local adaptation to thermal stress in two distant populations subjected to contrasting thermal and necrosis histories. No significant differences were found between populations. Colonies from both populations suffered no necrosis after long-term exposure to temperatures up to 29 °C. Second, we tested the effects of the interaction of both warming and the presence of invasive algae. The combined exposure triggered critical synergistic effects on photosynthetic efficiency and tissue necrosis. At the end of the experiment, over 90% of the colonies subjected to warming and invasive algae showed signs of necrosis. The results are of particular concern when considering the predicted increase of extreme climatic events and the spread of invasive species in the Mediterranean and other seas in the future

Marine heat waves detection in climate warming seas: their evolution in the NW Mediterranean sea

Ponencia presentada en: XII Congreso de la Asociación Española de Climatología celebrado en Santiago de Compostela entre el 19 y el 21 de octubre de 2022.[ES]El aumento extremo y prolongado de la temperatura del mar, una ola de calor marina (MHW), se detecta por comparación con los valores históricos en cada localización y época del año. Así, el correcto establecimiento de los valores de referencia es una tarea clave en la detección de MHW. Al comparar diferentes épocas es necesario considerar dos contribuciones a la evolución de los episodios extremos: la tendencia subyacente de la temperatura y los cambios súbitos de la misma. Siguiendo la definición de Hobday (2016), comparamos las MHW detectadas en caso de corregir o no la tendencia climatológica en la definición de los valores de referencia. Para ello empleamos 38 años de temperatura superficial del mar Mediterráneo proporcionados por el servicio Copernicus. El trabajo se centra alrededor de la reserva marina de las islas Columbretes, donde existe una estación costera de medición de la temperatura del mar integrada en la red T-MedNet. Esto permite vislumbrar el efecto a diferentes profundidades aunque con series temporales más cortas. El resultado es que no corregir la tendencia al definir la referencia subestima el número de eventos detectados en los primeros años de la serie y los sobreestima en los últimos, independientemente de la longitud de la serie. La influencia del cambio climático en la alteración de los ecosistemas marinos debido a las MHW no parece deberse al incremento en la frecuencia de las mismas, sino a que éstas tienen lugar en un mar cada vez más caliente, actuando sobre sistema biológicos con mayor estrés térmico.[EN]Extreme and prolonged increases in the sea temperature, a marine heatwave (MHW), are detected by comparison with historical values at each location and time of year. Thus, the correct estimation of reference values is key in detecting marine heatwaves. In temporally separated epochs comparison, it is necessary to consider two contributions to the evolution of extreme events: the underlying trend in temperature and its sudden changes. Following the definition of Hobday (2016), we compare the detected MHW in case of correcting or not the climatological trend in the definition of the reference values. We use 38 years of the surface temperature of the Mediterranean Sea provided by the Copernicus service. This work is centered around the Columbretes Islands marine reserve, where there is a coastal sea temperature measurement station integrated into the T-MedNet network. This allows us to have a glimpse of the effect at different depths but with shorter time series. The results show that if the long-term trend is not removed from the reference, then the number of events is underestimated in the first years of the series and overestimated in the last ones regardless of the length of the series. The influence of climate change on the alteration of marine ecosystems caused by the MHWs does not seem to be caused by the increased frequency of MHWs, but rather by the fact that the MHWs take place in an increasingly hot sea, acting on biological systems having greater thermal stress.This is a contribution made with the support of the MPA-Engage project (Grant:5216 | 5MED18_3.2_M23_007) and MINKE project (Grant: 101008724). The authors would like to thank the institutional support of the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S)

The emergent fouling population after severe eutrophication in the Mar Menor coastal lagoon

Mar Menor is one of the largest coastal lagoons in the Mediterranean basin. Over the years, Mar Menor has suffered a significant environmental degradation due to multiple factors with anthropogenic origin. The transformation from a rain-fed basin to intensive irrigated agriculture has led to an rise in the water inflow and nutrients in the basin, which has provoked severe eutrophication. The increase in nutrients led to changes in the structure and function of the lagoon ecosystems. The epibenthic and suspension feeder organisms have benefited from this imbalance, proliferating and reaching a high population density. The composition and abundance of the species assemblage found in the sub-coastal bottoms of the coastal lagoon after the environmental crisis occurred in 2016, using artificial settlement structures. The variation in community density and affinity between sampling sites in 2017 and 2018, were determined. A total of 31 species belonging to 27 genera and 7 phyla were observed in 11 samples. The best represented class are polychaeta (Phylum Annelida) with 11 identified species. The genus with the greatest species richness was Hydroides with two species: H. dianthus (Verrill, 1873), and H. elegans (Haswell, 1883), both of them considered potentially invasive and opportunistic species followed by the genus Serpula, with two species: S. vermicularis (Linnaeus, 1767), and S. concharum (Langerhans, 1880) and the genus Branchiomma was represented with another exotic invasive species, B. boholense (Grube, 1878), which is only found in collectors in 2018. These results have allowed to increase the knowledge about the effect of eutrophication in the structure of the fouling community in the assemblage succession in the Mar Menor coastal lagoon.This study was supported by the research fund of the University of Alicante and Murcia University Aquarium

Re-shifting the ecological baseline for the overexploited Mediterranean red coral

Overexploitation leads to the ecological extinction of many oceanic species. The depletion of historical abundances of large animals, such as whales and sea turtles, is well known. However, the magnitude of the historical overfishing of exploited invertebrates is unclear. The lack of rigorous baseline data limits the implementation of efficient management and conservation plans in the marine realm. The precious Mediterranean red coral Corallium rubrum has been intensively exploited since antiquity for its use in jewellery. It shows dramatic signs of overexploitation, with no untouched populations known in shallow waters. Here, we report the discovery of an exceptional red coral population from a previously unexplored shallow underwater cave in Corsica (France) harbouring the largest biomass (by more than 100-fold) reported to date in the Mediterranean. Our findings challenge current assumptions on the pristine state of this emblematic species. Our results suggest that, before intense exploitation, red coral lived in relatively high-density populations with a large proportion of centuries-old colonies, even at very shallow depths. We call for the re-evaluation of the baseline for red coral and question the sustainability of the exploitation of a species that is still common but ecologically (functionally) extinct and in a trajectory of further decline