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Too warm to be really pleasant: the unlucky tale of an E. singularis (Esper, 1791) retrieved on Torre Astura shores (Latium Coast, Central Tyrrhenian Sea)

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Eunicella singularis (Esper, 1791) is one of the most representative habitat-forming species of the rocky bottoms and Mediterranean coralligenous assemblages. This species is among the main representatives affected by the mass mortality events largely documented in several dive spots and marine research/fieldwork beaten areas over the last few decades. Currently E. singularis is mentioned among the vulnerable species of the IUCN Red List.From the very first records in 1999 up to the most recently published and ongoing research activities conducted in the marine environments a significant increasing of evidences of thermal-related stress have been recorded (Cerrano et al., 2005; Cerrano C. & Bavestrello G. 2008; Gambi et al., 2018).
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doi: 10.6084/m9.figshare.16726618
Gaglioti M.
SHORT COMMUNICATION
Too warm to be really pleasant: the unlucky tale of an E. singularis (Esper, 1791) retrieved on
Torre Astura shores (Latium Coast, Central Tyrrhenian Sea)
Introduction
Eunicella singularis (Esper, 1791) is one of the most representative habitat-forming species of the
rocky bottoms and Mediterranean coralligenous assemblages. This species is among the main
organisms affected by the mass mortality events largely documented in several dive spots and marine
research/fieldwork beaten areas over the last few decades. Currently E. singularis is mentioned
among the vulnerable species of the IUCN Red List.From the very first records in 1999 up to the
most recently published and ongoing research activities conducted in the marine environments a
significant increasing of evidences of thermal-related stress have been recorded (Cerrano et al., 2005;
Cerrano C. & Bavestrello G. 2008; Gambi et al., 2018).
An overall decline of more than 30% occurred in the last 20-30 years due to climate change for the
surface populations, while the deep forests are still very dense. According to their different tolerance
to thermal stress some studies suggest that deep-seated populations may belong to different species
(Ferrier-Pagès et al., 2009; Pey et al., 2011; Previati et al., 2010).
Material and methods
The stranded specimen has been classified on the basis of its morphological features and sampled
through visual and photographic methods. Some morphometric details have been noted (i.e. size and
degree of overall integrity) during the field observation. A GPS positioning of the stranding location
has been acquired through a mobile extension of the ESRI ArcGIS Collector for a more accurate
fieldwork database implementation and data collection.
Study Area
The occurrence of the stranded colony has been recorded along the littoral area of the Nettuno
municipality falling within the boundaries of the “Shoreline of Astura Tower” Site of Community
Interest (SCI IT6030048). The aforementioned SCI is located along the Latium coast in the nearby
of the Astura river. It belongs to the European “Natura 2000” Network, is almost entirely included
within the Neptune firing range and is owned by the Ministry of Defense, General Directorate of
Terrestrial Armaments, Territorial Technical Office of Terrestrial Armaments of Neptune
(U.T.T.A.T.). The “Astura Tower SCI” can be considered a relevant target for the implementation of
several conservation measures and research initiatives aimed at different habitats and relevant species
listed in the main EU Directives (92/43/CEE and 9/409/CEE). A wide range of habitats can be
distinguished in the SCI: from the pine forests covering up to 55% of the SCI area to the retrodunal
wetlands. There are also ancient and recent dune deposits and mainly sandy coastal wind deposits
consisting of complex and stable beach-dune systems, originating in coincidence with stretches of
low coast, contiguous towards the inland to plains and towards the sea at shallow depths. The limited
access number and the seasonal opening of the area for military reasons contributed to the
preservation of the site over the years. Despite it represents an area of high naturalistic value,
fundamental for relict biodiversity, today the effective conservation of the site is threatened from
multiple-driven impacts mainly related to relict unsustainable fishing practices, dumping events,
illegal practices aimed at removal of historical artifacts and unsustainable uses of the coastal
environment.
Sampling site
The sampling site (Lat. 41°24’30.78” N ; Long. 12°45’57.63” E) is located on the rocky bottoms in
the shallow waters surrounding the ancient remains of the roman fishponds in the left portion of the
beach between the “holed wall” of the roman ruins belonging to the ancient roman villa and the castle
(Fig.1, 2).
doi: 10.6084/m9.figshare.16726618
Figure 1,2 The coastal area in the nearby of the sampling site
Results
The collected fragment showed small traces of algal epibionts, maybe consequent to the colony
overall weakening induced by a prolonged thermal stress exposure of the hard skeleton before its
final detachment (Fig.3, 4).
Figure 3,4 The collected sample of E. singularis
Discussion
The occurrence of some mass mortality events or similarly-induced punctual strandings have been
recorded both through direct observations and indirect records gained through citizen science
contributions or public engagement initiatives happened in several coastal localities with the help of
some local stakeholders. An example is that of the citizen scientists involved in the self-funded
“(Sea)tizen Science” Project. According to the main principles stated in the Lima Action Plan the
main aim of this self-funded initiative was the engagement of the largest amount of people, including
bathers or occasional users of the littoral area between Sabaudia and Latina municipalities, in order
to raise their awareness on the marine biodiversity complexity and on the main issues currently
affecting the marine ecosystems and the overwhelming dynamics influencing their overall
functioning. Indeed, the suggested approach and “leitmotiv” of every proposed activity was the use
of local observations, hence made at a large-scale of detail, in order to think about the phenomena
acting locally “in the sea of our backyard” due to the same trends acting more widely at a global scale
level.
doi: 10.6084/m9.figshare.16726618
Similar occurrences have been highlighted also in neighboring areas of Latium region except from
“Torre Astura” and the Circeo MaB Reserve in the last few years. This trend reflects the observations
widely documented also for other areas of the Mediterranean basin and currently under rigorous
monitoring for larger-scale understandings. In this case we have no information on the effective
settlement depth and the features of the original site hosting the collected branches, even though the
way of the occurrence is not different from the previously documented observation happened
similarly on the sandy shores of a neighboring area falling within the buffer zone of the Circeo Man
and Biosphere Reserve (Gaglioti M., pers. obs. February-March 2020; Fig. 5a, b).
Figure 5 (a, b) The E. singularis sample collected on the shores of the Circeo MaB Reserve on 3.3.2021
The very shallow waters around the last observation location (Lat. 41°24’30.78” N; Long.
12°45’57.63” E) are mainly characterized by phytophilous algae covering and organisms of the
intertidal and subtidal rocky bottoms communities. There are no evidences of gorgonians in the very
few meters off the shore, even though several spots suitable for diving and spearfishing activities
located few nautical miles apart are known. These are characterized by the presence of spotty and
degraded coralligenous outcrops, due to the persistence of poorly sustainable fishing practices
occurred in the last few decades both on soft bottoms and hard substrates’ assemblages in the
surrounding areas of the coastal zone.
The occurrence of the last observed beached colony can be a plausible outcome of a current-driven
transport consequent to a detachment due to a pervasive necrosis and mortality event enhanced by a
prolonged high temperature and water column stratification in the shallow waters in the nearby of the
sampling area. The mean surface temperature recorded was around 24-25°C both in the observation
day (19.9.2021; Fig. 6 a,b, c) and in the previous weeks (28-30.08.2021; Fig. 7 a, b).
Figure 6 (a, b, c) The observation conducted on 19.9.2021 (Sea surface temperature 25°C)
b
a
c
a
b
doi: 10.6084/m9.figshare.16726618
Figure 7 (a, b) The previous observation conducted on 30.8.2021 (Sea surface temperature 24°C)
References
Cerrano, C., Arillo, A., Azzini, F., Calcinai, B., Castellano, L., Muti, C., ... & Bavestrello, G. (2005). Gorgonian
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15(2), 147-157.
Cerrano, C., & Bavestrello, G. (2008). Medium-term effects of die-off of rocky benthos in the Ligurian Sea. What
can we learn from gorgonians? Chemistry and Ecology, 24(S1), 73-82.
Ferrier-Pagès, C., Tambutté, E., Zamoum, T., Segonds, N., Merle, P. L., Bensoussan, N., ... & Tambutté, S.
(2009). Physiological response of the symbiotic gorgonian Eunicella singularis to a long-term temperature
increase. Journal of Experimental Biology, 212(18), 3007-3015.
Gambi et al. (2018) Mortality events of benthic organisms along the coast of Ischia in summer 2017 Biol. Mar.
Mediterr. (2018), 25 (1): 212-213.
Pey A, Zamoum T, Allemand D, Furla P, Merle P-L (2011) Depth-dependant thermotolerance of the symbiotic
Mediterranean gorgonian Eunicella singularis: Evidence from cellular stress markers. Journal of Experimental
Marine Biology and Ecology 404: 7378.
Previati M, Scinto A, Cerrano C, Osinga R (2010) Oxygen consumption in Mediterranean octocorals under
different temperatures. Journal of Experimental Marine Biology and Ecology 390: 3948.
This work can be mentioned as:
Gaglioti M. (2021) Too warm to be really pleasant: the unlucky tale of an E. singularis (Esper, 1791)
retrieved on Torre Astura shores (Latium Coast, Central Tyrrhenian Sea) doi: 10.6084/m9.figshare.16726618
This contribution is the outcome of a self-funded research initiative and is currently distributed under CC
License 4.0 CC-BY-NC-ND
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