Distribution patterns of the cardinal fish Apogon imberbis (Linnaeus, 1758) within Mediterranean marine caves and its potential role for cave ecosystem functioning
-
1
Université Nice Sophia Antipolis, UCA, CNRS, France
-
2
Consorzio Interuniversitario per le Scienze del Mare, CoNISMa, Italy
-
3
USR 3278 CNRS-EPHE, Université de Perpignan, France
Along the coasts of the Mediterranean Sea, marine caves are widespread and often unexplored. They host well diversified, unique and sensitive biological communities, due to the special ecological conditions inside (e.g. patterns of light extinction, water motion and distribution of trophic resources), and to the fact that many organisms living inside marine caves are extremely fragile or shy.
Spatial distribution of organisms inside the caves is not homogeneous. The algae only occur in the initial portions, where there is sufficient light to support photosynthesis. Inside, unexpectedly diversified communities of sessile animals fixed on the substrate cover most of the available substrate.
Marine caves are also inhabited by juveniles and adults of vagile species, including commercial fishes. Several coastal fishes, in fact, can be found inside marine caves in the Mediterranean Sea, encompassing (1) species exclusively associated to marine caves, (2) species generally typical of cryptic habitats, and (3) nectobenthic species generally associated to rocky reefs that can be found occasionally within caves, often in their initial portions.
The relevance of studying communities of marine organisms living into marine caves is chiefly related to their intrinsic value in terms of contribution to coastal marine biodiversity. Such communities include a number of fragile and shy species exposed to dangerous impacts (e.g. divers’ frequentation). This is the reason why: (1) marine caves are among the few marine habitats under protection for the European Community (Habitat Directive 92/43EEC); (2) some recent studies suggested the systematic inclusion of marine caves into Marine Protected Areas’ designs.
The chances to push for more effective protection and management of Mediterranean marine caves passes also throughout the possibility to improve the knowledge on their communities and ecosystem functioning. There are some aspects, in particular about functioning, on which the available knowledge is scanty. This is the case of the possible trophic connectivity “inside-outside”, which represents the potential mechanism through which the primary production taking place outside caves could support marine communities inside. Some studies have documented the trophic role of cave-dwelling mysids, which could transfer, via their nictemeral migrations, particulate organic matter (POM) inside caves. A similar role has been also hypothesized for the cardinal fish Apogon imberbis, which could get out from the caves during the night to feed, to then get back into the caves at dawn (nictemeral migration), deposing its dejections (i.e. valuable food source in the form of POM) daytime inside the caves. This process could help mitigate the oligotrophic conditions inside caves. One important point to support this hypothesis is related to the abundance and biomass of A. imberbis: only if or where populations of this fish show significant abundances and biomasses, then its trophic role can be relevant for sustaining marine cave communities.
This study, therefore, is aimed at investigating 1) the relative contribution of A. imberbis in terms of abundance and biomass of fish assemblages, and 2) its distribution patterns at multiple spatial scales, within 16 marine caves along the Mediterranean coasts of Spain, France and Italy.
Fish sampling was carried out in June-August 2015 in 16 semi-submerged or submerged caves located in 6 zones: 3 caves at Cap de Creus (Spain), 3 at Côte Bleue and 3 at Villefranche (France), 2 at Tavolara Island, 2 at Bergeggi and 3 at Ventimiglia (Italy). The investigated caves encompassed blind caves (one entrance) and caves with several openings, remarkably varying in morphology, branching and overall extension, presence/absence of an underwater ceiling, and characteristics of the bottom (e.g. formed by rocks or sandy/muddy sediments), within the bathymetric range 3-24 m.
Fish density was estimated using a modified transect visual census method using SCUBA. Transects were 5 to 25 m long and 2 m wide, as transect length was adapted to the shape and morphological discontinuities of each cave and internal sector. The number of transects performed in each cave was variable in relation to the extent and topography. A total of n = 67 visual censuses were performed in the present study. Fish biomass was calculated on the basis of the best available length/weight relationships (www.fishbase.org). Due to the variable dimensions of transects, abundance and biomass values were converted to 100 m2.
In order to investigate spatial variability in both A. imberbis density and biomass, we carried out two permutational analyses of variance (PERMANOVA) using an experimental design encompassing two factors: Zone (Zo, random, 6 levels) and Cave (Ca, random, nested in Zo, 2-3 levels).
The analyses showed consistency in spatial patterns between density and biomass, with no significant difference among caves within each zone, and a highly significant difference among zones (p<0.01 for both density and biomass) (Tab. 1).
The cardinal fish was in absolute the most frequent fish species: it was the only fish recorded in all the marine caves studied, and in 91% of UVCs we have carried out in the present study. In terms of density of individuals, the cardinal fish represented 74.2 ± 5.2 % (mean ± SE; ranging from 12 to 93% depending on the cave) of all fishes censused in each cave. In terms of biomass, it accounted for 29.2 ± 4.2% (mean ± SE; ranging from 12 to 93%, depending on the cave) of the whole fish biomass estimated into the 16 studied caves.
In conclusion, these data show that density and biomass of the cardinal fish A imberbis 1) are highly variable at a large spatial scale (i.e. among the 6 zones investigated) while they are consistent at smaller spatial scale (i.e. among caves within each zone), and 2) are higher than those of any other fish species we have censused into marine caves in our study carried out in the NW Mediterranean Sea. Even though other evidences are need (e.g. a significant nictemeral movement or an effective feeding on prey associated to habitats outside the caves have not been demonstrated yet), the evidence provided by this study supports the hypothesis that the cardinal fish, due to its abundance and biomass, could have the potential to fulfill a crucial trophic role within marine caves.
Acknowledgements
This research was funded by Total Foundation (http://fondation.total.com/fr). The funder had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. The authors wish to thank the staff of the Tavolara-Punta Coda Cavallo, Bergeggi Island, Cap de Creus and Côte Bleue MPAs for their support.
Keywords:
Marine caves,
fiah ecology,
Cardinal fish,
Apogon imberbis,
trophic ecology
Conference:
IMMR | International Meeting on Marine Research 2016, Peniche, Portugal, 14 Jul - 15 Jul, 2016.
Presentation Type:
Poster presentation
Topic:
Biodiversity, Conservation and Coastal Management
Citation:
Bussotti
S,
Di Franco
A,
Pey
A,
Vieux
J,
Planes
S and
Guidetti
P
(2016). Distribution patterns of the cardinal fish Apogon imberbis (Linnaeus, 1758) within Mediterranean marine caves and its potential role for cave ecosystem functioning.
Front. Mar. Sci.
Conference Abstract:
IMMR | International Meeting on Marine Research 2016.
doi: 10.3389/conf.FMARS.2016.04.00078
Copyright:
The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers.
They are made available through the Frontiers publishing platform as a service to conference organizers and presenters.
The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated.
Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed.
For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions.
Received:
17 Apr 2016;
Published Online:
13 Jul 2016.
*
Correspondence:
Prof. Paolo Guidetti, Université Nice Sophia Antipolis, UCA, CNRS, Nice, 06108, France, guidetti@unice.fr