Project “Biodiversity MARE Tricase”: A Species Inventory of the Coastal Area of Southeastern Salento (Ionian Sea, Italy)

Biodiversity is a broad concept that encompasses the diversity of nature, from the genetic to the habitat scale, and ensures the proper functioning of ecosystems. The Mediterranean Sea, one of the world’s most biodiverse marine basins, faces major threats, such as overexploitation of resources, pollution and climate change. Here we provide the first multi-taxa inventory of marine organisms and coastal terrestrial flora recorded in southeastern Salento (Ionian Sea, Italy), realized during the project “Biodiversity MARE Tricase”, which provided the first baseline of species living in the area. Sampling was carried out by SCUBA and free diving, fishing gears, and citizen science from 0 to 70 m. Overall, 697 taxa were found between March 2016 and October 2017, 94% of which were identified to the species level. Of these, 19 taxa represented new records for the Ionian Sea (36 additional new records had been reported in previous publications on specific groups, namely Porifera and Mollusca Heterobranchia), and two findings represented the easternmost records in the Mediterranean Sea (Helicosalpa virgula and Lampea pancerina). For eight other taxa, our findings represented the only locality in the Ionian Sea, besides the Straits of Messina. In addition to the species list, phenological events (e.g., blooms, presence of reproductive traits and behaviour) were also reported, with a focus on gelatinous plankton. Our results reveal that even for a relatively well-known area, current biodiversity knowledge may still be limited, and targeted investigations are needed to fill the gaps. Further research is needed to understand the distribution and temporal trends of Mediterranean biodiversity and to provide baseline data to identify ongoing and future changes

Effects of anthropogenic stressors on temperate mesophotic ecosystems

Coastal ecosystems are among the most productive biomes on the planet, but also the most vulnerable. A wide range of anthropogenic impacts are threatening the integrity of coastal systems, and therefore their capability to provide goods and ecosystem services. Despite their importance and vulnerability, many coastal ecosystems remain poorly studied. Mesophotic ecosystems lie between the shallow euphotic waters and the aphotic deep-sea. While these ecosystems have been relatively well-studied in tropical regions, the importance of temperate mesophotic ecosystems (TMEs) has only recently been recognised. TMEs extend from the lower limit of the euphotic zone to the limit of benthic primary production, which usually correspond to ~30–150 m. However, in particular conditions, mesophotic ecosystems can occur in shallower waters. Lough Hyne (Ireland) is a fully marine sea lough, designated as Europe's first Marine Nature Reserve in 1981 for its extraordinary biodiversity. This reserve hosts particularly diverse sponge-dominated mesophotic communities as shallow as 10 m. Unfortunately, during the last decade, the lough’s underwater communities have undergone drastic changes, which have been attributed to changes in water quality and in particular, an increase in dissolved nitrogen. My research aimed to investigate the effects of anthropogenic stressors on temperate mesophotic ecosystems using Lough Hyne as a model system. My thesis aims to: 1) characterise the changes that have occurred in the subtidal communities at Lough Hyne; 2) investigate the possible causes of these changes through tolerance experiments; and 3) investigate community dynamics and any recovery of Lough Hyne’s mesophotic communities. In my first chapter, I collated 30 years (1990-2019) of scientific surveys and opportunistic observations of the subtidal (6–30 m) communities at Lough Hyne to investigate the long-term stability and vulnerability of TMEs. I then explored the potential causes of the observed changes. I found significant changes in the overall biological community and sponge assemblages at all sites within Lough Hyne. However, these changes were not consistent across sites and mainly affected the innermost areas of the lough. Changes were also not consistent between taxa and functional groups, suggesting differential vulnerability of TME organisms to stress events. The main finding was a marked decline in most three-dimensional sponges in the inner part of the lough, which was likely the result of one or more mass mortality events between 2010 and 2015. These changes did not seem to be related to either thermal or rainfall anomalies. The only factor known to have changed over this period is nitrogen, which has increased threefold during the last 20-30 years. Therefore, I hypothesised that the sponge mortality at Lough Hyne is linked to eutrophication. Importantly, this chapter shows the potential vulnerability of TMEs to short-term disturbance events, and highlights the importance of monitoring mesophotic habitats globally to ensure they are appropriately conserved. In my second chapter, I investigated the possible causes of the mass sponge mortality at Lough Hyne through laboratory experiments. One of the most common and severe consequences of eutrophication in aquatic ecosystems is hypoxia. Therefore, I investigated the response of sponges to moderate and severe simulated hypoxic events. I ran three laboratory experiments on four species from two different temperate oceans (NE Atlantic and SW Pacific). I exposed sponges to a total of five hypoxic treatments, with increasing severity (3.3, 1.6, 0.5, 0.4 and 0.13 mg O2 L-1, over 7–12 days). The main finding was that sponges are generally very tolerant of hypoxia. All sponges survived under the experimental conditions, except Polymastia croceus, which showed significant mortality at the lowest oxygen concentration (0.13 mg O2 L-1, median lethal time: 12 days). In all species except Suberites carnosus, respiration rate was unaffected down to 0.4 mg O2 L-1. Importantly, sponges showed species-specific phenotypic changes in response to hypoxic treatments, likely representing adaptive strategies for living in low oxygen water. Compared to other sessile organisms, sponges generally showed a much higher tolerance to hypoxia, suggesting that sponges may be favoured and survive in future deoxygenated oceans. These results also indicate that hypoxia alone was probably not the cause of sponge mortality at Lough Hyne. In my third data chapter, I investigated the resilience and temporal dynamics of shallow-water (~ 17 m) mesophotic communities at Lough Hyne, following the mass mortality event. In June 2018, I established five replicate permanent quadrats (0.25 m2) on the rocky cliffs (18 m) at five sites inside the lough. My collaborators and I took photoquadrats twice a year until June 2021 (36 months, 5–7 time points), from which I extracted data on the percentage cover of sessile organisms identified to the lowest practical taxonomic level. In addition, I analysed historical photoquadrats collected with a similar methodology between 1994 and 1995, from two internal sites at Lough Hyne. Historical data were used to assess if differences in temporal patterns between sites were exclusive to impacted communities or also occurred in the past. Multivariate analysis did not detect any directional community or assemblage changes over time in the internal and innermost sites, suggesting that recovery of benthic communities and sponge assemblages is either occurring very slowly or not at all. In contrast, I found significant community changes at the entrance site, where barnacles suffered a mass mortality event in 2018, perhaps due to a heatwave. Univariate analysis revealed weak signs of recovery for some of the three-dimensional sponges and anemones that were highly affected by the disturbance, represented by a small increase in percentage cover. In general, temporal dynamics (turnover, diversity and percentage cover of benthic groups) were found to be different between: 1) sites experiencing very distinct environmental conditions; and 2) between sites that shared similar conditions and communities. Most importantly, sponges seem to be recovering only in one of the three internal sites, where I detected a positive trend in the three-dimensional sponges affected by the 2010–2015 mortality event. This finding indicates that small variations in environmental conditions can affect the dynamics and recovery of mesophotic subtidal ecosystems. Overall, my thesis shows that mesophotic ecosystems are vulnerable to environmental stressors and slow recovery rates. Most temperate mesophotic taxa are long-lived and slow-growing organisms, likely to have limited resilience to human-induced impacts. Despite sponges being generally considered tolerant of stressors, the mass mortality at Lough Hyne shows that this is not always the case. My results suggest that three-dimensional mesophotic sponges are among the most sensitive species and the slowest growing. Any decline in these habitat-forming species will likely affect important ecosystem functions (e.g., nutrient cycling, bentho-pelagic coupling, habitat provisioning), with detrimental effects on the associated ecosystem services. My study also shows that, as some sites, recovery is underway. However, at the current rate, whole-lough recovery is likely to be in the order of decades. Given the vulnerability and importance of TMEs, research and management of these habitats should be prioritised at Lough Hyne and elsewhere. In particular, long-term monitoring of biotic and abiotic factors will be crucial to understand TME long-term dynamics, recovery and how these ecosystems respond to environmental variations and anthropogenic disturbances. Monitoring will improve our ability to make evidence-based decisions for the management of TMEs in a fast-changing world. In addition, we also need more research on how mesophotic organisms respond to stressors and how they contribute to ecosystem functioning. Better knowledge of these ecosystems will increase awareness of the value of TMEs among decision-makers and the general public, which will be essential to ensure their conservation.</p

Reproduction and early life stages of the poecilosclerid sponge Crella incrustans

Este artículo contiene 13 páginas, 5 figuras, 1 tabla.Despite their important ecological roles in marine ecosystems, reproduction and early life stages of the majority of marine sponges remain undescribed. Here we characterize the mode of reproduction and the early life stages of an abundant sponge in temperate Pacific waters, Crella incrustans. Through histology, we characterized the production of gametes and the sequential steps of larval ontogeny. Using in vivo observations, we described larval release, settlement, and metamorphosis. Specimens of C. incrustans presented spermatocytes, oocytes, and several developmental stages in the sponge mesohyl during the Australasian summer (from January to March 2020), demonstrating this sponge to be a simultaneous hermaphrodite with internal fertilization, asynchronous development, and brooded embryos. As in other viviparous demosponges, mature embryos were released during the Australasian summer as free-swimming non-tufted parenchymella larvae. Under laboratory conditions, 94.3% of larvae settled within 2 days and metamorphosed into functional settlers within a week. Gametogenesis, embryonic development, larval characteristics, settlement, and metamorphosis of C. incrustans are consistent with the reproductive features common to the majority of poecilosclerid sponges. Overall, our study provides important information on the early life stages of this temperate model species for future ecophysiological experiments.This work was supported by the Victoria University Doctoral Scholarship and the Women Divers Hall of Fame Graduate Scholarship in Marine Conservation 2020 awarded to Francesca Strano.Peer reviewe

Shallow-water sponge grounds along the Apulian coast (central Mediterranean Sea)

Sponge grounds are complex three-dimensional benthic habitats dominated by sponges. These sponge-dominated assemblages have been reported worldwide, from the intertidal zone to the deep sea. In shallow euphotic waters, dense sponge aggregations have been mainly found in tropical areas, and their presence is in some cases related to environmental degradation and coral decline. The Mediterranean Sea is globally recognised as a biodiversity hotspot, where light-exposed rocky reefs are typically dominated by photophilous algae. However, high local anthropogenic pressures, coupled with climate change, are leading to the reorganisation of benthic communities and the occurrence of regime shifts in several areas. Here we report the first description of unusual, shallow-water sponge grounds in Mediterranean light-exposed rocky reefs, in an area previously impacted by the destructive date-mussel fishery. These assemblages, found along the Apulian coast (central Mediterranean Sea), are now (2017) characterised by a mean coverage of sponges ranging between 3% and 33%, with maximum values up to 85%. Variation in the structure of assemblages and in the abundance of individual taxa between depths has been tested by multivariate and univariate techniques. The spatial characterisation has been complemented with the taxonomic analysis of the sponge assemblages, which resulted in the identification of 14 sponge taxa. These findings are compared with results of previous research in the same area and discussed with particular reference to the potential variables involved in sponge dominance and spatial distribution in the present system and elsewhere

Adaptive strategies of sponges to deoxygenated oceans

Ocean deoxygenation is one of the major consequences of climate change. In coastal waters, this process can be exacerbated by eutrophication, which is contributing to an alarming increase in the so-called ‘dead zones’ globally. Despite its severity, the effect of reduced dissolved oxygen has only been studied for a very limited number of organisms, compared to other climate change impacts such as ocean acidification and warming. Here, we experimentally assessed the response of sponges to moderate and severe simulated hypoxic events. We ran three laboratory experiments on four species from two different temperate oceans (NE Atlantic and SW Pacific). Sponges were exposed to a total of five hypoxic treatments, with increasing severity (3.3, 1.6, 0.5, 0.4 and 0.13 mg O2 L−1, over 7–12-days). We found that sponges are generally very tolerant of hypoxia. All the sponges survived in the experimental conditions, except Polymastia crocea, which showed significant mortality at the lowest oxygen concentration (0.13 mg O2 L−1, lethal median time: 286 h). In all species except Suberites carnosus, hypoxic conditions do not significantly affect respiration rate down to 0.4 mg O2 L−1, showing that sponges can uptake oxygen at very low concentrations in the surrounding environment. Importantly, sponges displayed species-specific phenotypic modifications in response to the hypoxic treatments, including physiological, morphological and behavioural changes. This phenotypic plasticity likely represents an adaptive strategy to live in reduced or low oxygen water. Our results also show that a single sponge species (i.e., Suberites australiensis) can display different strategies at different oxygen concentrations. Compared to other sessile organisms, sponges generally showed higher tolerance to hypoxia, suggesting that sponges could be favoured and survive in future deoxygenated oceans

Sponge functional roles in a changing world

Sponges are ecologically important benthic organisms with many important functional roles. However, despite increasing global interest in the functions that sponges perform, there has been limited focus on how such functions will be impacted by different anthropogenic stressors. In this review, we describe the progress that has been made in our understanding of the functional roles of sponges over the last 15 years and consider the impacts of anthropogenic stressors on these roles. We split sponge functional roles into interactions with the water column and associations with other organisms. We found evidence for an increasing focus on functional roles among sponge-focused research articles, with our understanding of sponge-mediated nutrient cycling increasing substantially in recent years. From the information available, many anthropogenic stressors have the potential to negatively impact sponge pumping, and therefore have the potential to cause ecosystem level impacts. While our understanding of the importance of sponges has increased in the last 15 years, much more experimental work is required to fully understand how sponges will contribute to reef ecosystem function in future changing oceans

Project &ldquo;Biodiversity MARE Tricase&rdquo;: A Species Inventory of the Coastal Area of Southeastern Salento (Ionian Sea, Italy)

Biodiversity is a broad concept that encompasses the diversity of nature, from the genetic to the habitat scale, and ensures the proper functioning of ecosystems. The Mediterranean Sea, one of the world&rsquo;s most biodiverse marine basins, faces major threats, such as overexploitation of resources, pollution and climate change. Here we provide the first multi-taxa inventory of marine organisms and coastal terrestrial flora recorded in southeastern Salento (Ionian Sea, Italy), realized during the project &ldquo;Biodiversity MARE Tricase&rdquo;, which provided the first baseline of species living in the area. Sampling was carried out by SCUBA and free diving, fishing gears, and citizen science from 0 to 70 m. Overall, 697 taxa were found between March 2016 and October 2017, 94% of which were identified to the species level. Of these, 19 taxa represented new records for the Ionian Sea (36 additional new records had been reported in previous publications on specific groups, namely Porifera and Mollusca Heterobranchia), and two findings represented the easternmost records in the Mediterranean Sea (Helicosalpa virgula and Lampea pancerina). For eight other taxa, our findings represented the only locality in the Ionian Sea, besides the Straits of Messina. In addition to the species list, phenological events (e.g., blooms, presence of reproductive traits and behaviour) were also reported, with a focus on gelatinous plankton. Our results reveal that even for a relatively well-known area, current biodiversity knowledge may still be limited, and targeted investigations are needed to fill the gaps. Further research is needed to understand the distribution and temporal trends of Mediterranean biodiversity and to provide baseline data to identify ongoing and future changes

Project “Biodiversity MARE Tricase”: biodiversity research, monitoring and promotion at MARE Outpost (Apulia, Italy).

none21noThe project “Biodiversity MARE Tricase” aims to research and promote coastal and marine biodiversity at the MARE Outpost (Avamposto MARE), a marine station established in Tricase (Lecce, Italy) in 2015. From March 2016 to September 2017, the first biodiversity inventory of the Tricase coastal area (Ionian Sea) was realized with the aid of citizen scientists (e.g. local fishermen, divers, bathers, and tourists). Preliminary results include 556 taxa, of which the 95% were identified at the species level. Despite the broad knowledge on Mediterranean coastal biodiversity, 71 species represented new records for the Ionian Sea. In parallel with the research activities, people’s awareness of the value of biodiversity was raised with scientific dissemination initiatives, involving about 1700 people. The “Biodiversity MARE Tricase” project realized a first small-scale species inventory contributing to the distributional, taxonomic, and ecological knowledge of the present Mediterranean biota. The coastal area of Tricase will be soon included in a new Marine Protected Area and this project represents a step forward for the sustainable development of the community of this coast.noneMicaroni, V.; Strano, F.; Di Franco, D.; Langeneck, J.; Gravili, C.; Bertolino, M.; Costa, G.; Rindi, F.; Froglia, C.; Crocetta, F.; Giangrande, A.; Nicoletti, L.; Medagli, P.; Zuccarello, V.; Arzeni, S.; Bo, M.; Betti, F.; Mastrototaro, F.; Lattanzi, L.; Piraino, S.; Boero, F.Micaroni, V.; Strano, F.; Di Franco, D.; Langeneck, J.; Gravili, C.; Bertolino, M.; Costa, G.; Rindi, F.; Froglia, C.; Crocetta, F.; Giangrande, A.; Nicoletti, L.; Medagli, P.; Zuccarello, V.; Arzeni, S.; Bo, M.; Betti, F.; Mastrototaro, F.; Lattanzi, L.; Piraino, S.; Boero, F