Distribution patterns of intertidal zoantharian species in the Canary Islands and their relation with ocean temperature
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1
Universidad de La Laguna, Spain
Global warming is driving changes in the distribution patterns of many species, leading to a tropicalization and meridionalization of the biota. In this context, populations of some marine species are in current regression while others favoured by temperature increases are expanding their populations. Such is the case of benthic cnidarians belonging to the order Zoantharia and suborder Brachycnemina, whose populations are able to cause phase-shifts in corals reefs ecosystems (Cruz et al. 2016). Marine assemblages at the subtropical region of the Canary Islands consist of a combination of both temperate and tropical species (Brito et al. 2005), mainly due to the east-to-west seawater temperature (SST) gradient that naturally exists throughout the Archipelago (23-25ºC in summer) (Figure 1a). Therefore, it constitutes a unique emplacement to study any biota reorganization processes due sea water warming. The aim of this study was to create a baseline of the distribution of intertidal zoantharian populations in relation to the temperature gradient along the Canary Islands.
Surveys were conducted during 2015-2016 throughout the Archipelago at intertidal rocky platforms where zoantharian species could inhabit (Figure 1b). Surveys consisted in exhaustive search through the entire study area during monthly spring low tide by at least two people. Differences in zoantharian assemblages among the different islands were assessed by means of permutational multivariate analysis of variance (PERMANOVA). Species-specific abundance analyses were also performed with permutational ANOVAs. In all previous analyses, the size of the intertidal rocky platform surveyed at each location was taken into account as a covariable.
Five intertidal Zoantharia species belonging to suborder Brachycnemina were recorded along the Archipelago: Palythoa aff. clavata, P. caribaeorum, P. grandiflora, Zoanthus pulchellus and Isaurus tuberculatus. Species identifications were sensu López et al. (2019). Additionally, 15 specimens of an unknown species were registered in Matas Blancas, Fuerteventura Island (Figure 1b). Although genetic analyses are necessary for an accurate species identification, external morphological features matched Terrazoanthus Reimer & Fujii, 2010 (suborder Macrocnemina), constituting the first record of this genus in the Canary Islands.
A total of 2208 zoantharian colonies were recorded, being P. aff. clavata the dominant species (1754 colonies) that was registered in all islands (Figure 1b). The analysis of the abundance and composition of zoantharian assemblages showed a significant effect of factor “Island” (F= 2.05; p=0.024), highlighting significant differences in assemblages found in the coldest eastern island of Lanzarote (Figure 1a,b), in contrast to the other islands of the Archipelago (Figure 1b). Species-specific analyses of P. aff. clavata showed a significant effect of the interaction between factor ‘Island’ and covariable “Platform size” (F= 5.09; p=0.003). Densities found in La Graciosa were significantly higher than in the rest of islands, while abundances within Lanzarote were significantly lower (Figure 1b). Despite rocky platforms of La Palma, La Gomera and El Hierro are noticeably narrower than in the rest of islands, which reduces habitat availability, not differences in the density of P. aff. clavata were detected between these islands and Tenerife, Gran Canaria and Fuerteventura. In the case of the latter islands, the species also showed warm waters affinities showing higher abundances restricted to the warmest locations as well as in the widest intertidal platforms (Figure 1a,b). In the case of P. caribaeorum, no effect of “Island” but a significant effect of “Platform size” (F= 7.73; p=0.049) was detected over abundances. The two largest populations of the species were recorded in Lanzarote and Fuerteventura (Figure 1b) in extremely large and elevated rocky platforms which, combined to the wide tidal amplitude experienced in these islands (up to -1.8 m), leaves many tidepools separated from the open ocean and heating for several hours during low tide. These particular characteristics may explain why thermophilic P. caribaeorum is able to inhabit in the intertidal zone of the eastern colder islands of the Canaries. What is more, the other intertidal population of P. caribaeorum is almost restricted the warmest western coast of Tenerife, with only one extra colony that has been recently found in the southeastern coast (Figure 1b). This may be the result of a recent expansion of this species related to sea water warming.
The distribution of I. tuberculatus did not show differences between studied islands, but a marginally significant effect of “Platform size” (F= 3.70; p=0.073) was observed. Discrete colonies were restricted to the low intertidal of the largest rocky platforms of Tenerife, Lanzarote and Gran Canaria, locations characterised by high hydrodynamic levels. P. grandiflora and Z. pulchellus were only recorded in Tenerife and, although P. grandiflora was registered in the warmest coast of the island, its relation to SST cannot be addressed since only one population was found. Z. pulchellus seemed to be also restricted to specific locations with the two largest populations recorded in the northern coast of Tenerife (Figure 1b), covering huge extensions over rocky platforms.
We found clear distribution patterns related to the SST gradient throughout the Canary Islands only for intertidal populations of P. aff. clavata and P. caribaeorum. Other factors such as specific habitat features or interspecific interactions may be responsible for the abundance of other zoantharian species. Therefore, effective monitoring programs are recommended only for P. aff. clavata and P. caribaeorum populations in order to early detect any possible population expansions or even phase-shifts mediated by sea water warming that might lead to significant changes in ecosystems dynamics.
Figure 1: Image of sea water temperatures (SST) recorded around the Canary Islands in summer time generated by satellites AVHRR/NOAA, showing the east-west gradient due to the influence of the Saharian upwelling (a). Distribution and abundances of zoantharian species around intertidal habitats throughout the Canary Islands: La Palma (LP), El Hierro (EH), La Gomera (GO), Tenerife (TF), Gran Canaria (GC), Fuerteventura (FV), Lanzarote (LZ) and La Graciosa (LG)
Acknowledgements
This study has benefited from the development of the MIMAR MAC/4.6.d/066 project (INTERREG MAC 2014-2020) and public contributions to the Canarian Government RedPromar network. C. López was co-funded by the Canarian Agency for Research, Innovation and Information Society of the Ministry of Economy, Industry, Trade and Knowledge and by the European Social Fund (ESF) integrated operational program of the Canary Islands 2014–2020
References
Brito A, Falcón JM, Herrera R (2005) Sobre la tropicalización reciente de la ictiofauna litoral de las islas Canarias y su relación con cambios ambientales y actividades antrópicas. Vieraea 33: 515–526
Cruz ICS, Kikuchi RK, Creed JC (2016). Ecological processes of phase shift to Palythoa grandiflora dominance on reefs of Todos-os-Santos Bay, Brazil. Front Mar Sci Conference Abstract: XIX Iberian Symposium on Marine Biology Studies. doi: 10.3389/conf.FMARS.2016.05.00050
López C, Reimer JD, Brito A, Simón D, Clemente S, Hernández M (2019) Diversity of zoantharian species and their symbionts from the Macaronesian and Cape Verde ecoregions demonstrates their widespread distribution in the Atlantic Ocean. Coral Reefs 38: 269–283
Keywords:
Coastal zone,
Bioindicator,
Palythoa spp.,
ocean warming,
Monitoring
Conference:
XX Iberian Symposium on Marine Biology Studies (SIEBM XX) , Braga, Portugal, 9 Sep - 12 Sep, 2019.
Presentation Type:
Oral Presentation
Topic:
Global Change, Invasive Species and Conservation
Citation:
Batista
CL,
Fernández Martín
S,
Moreno-Borges
S,
Rodríguez
A and
Clemente
S
(2019). Distribution patterns of intertidal zoantharian species in the Canary Islands and their relation with ocean temperature.
Front. Mar. Sci.
Conference Abstract:
XX Iberian Symposium on Marine Biology Studies (SIEBM XX) .
doi: 10.3389/conf.fmars.2019.08.00047
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Received:
15 May 2019;
Published Online:
27 Sep 2019.
*
Correspondence:
Miss. Cataixa L Batista, Universidad de La Laguna, San Cristóbal de La Laguna, Spain, kattaissa@gmail.com