Influence of anthropogenic factors in the community of loggerhead sea turtles (Caretta caretta) in Portuguese continental waters
Lidia
V.
Nicolau1, 2*,
Ana
Marçalo3,
Marisa
Ferreira1,
Silvia
Monteiro2,
Sara
Sá1, 2,
Andreia
T.
Pereira1, 4,
Jorge
Santos1, 5, 6,
Hélder
Araújo1, 5, 6,
Marina
Sequeira7,
José
Vingada1 and
Catarina
Eira1, 2
-
1
Sociedade Portuguesa de Vida Selvagem, Portugal
-
2
Centre for Environmental and Marine Studies, Department of Chemistry, University of Aveiro, Portugal
-
3
Center of Marine Sciences (CCMAR), Portugal
-
4
Centro de Estudos do Ambiente e do Mar, Faculdade de Ciências da Universidade de Lisboa, Portugal
-
5
Independent researcher, Spain
-
6
Other, Portugal
-
7
Instituto da Conservação da Natureza e das Florestas (ICNF), Portugal
Among marine megafauna, sea turtles were highly impacted by anthropogenic activities. The most significant threats include direct take, coastal development, pollution and pathogens, global warming and the impact of fisheries. Sea turtles are protected by various international protocols, including CITES, the Bonn Convention, The Bern Convention and the Habitats Directive. This work shed light onto various aspects of the ecology of loggerhead sea turtles (Caretta caretta) along the Portuguese coast, where information was previously very scarce. For this species, some aspects related to its distribution and cause of strandings, diet and major threats were evaluated in order to promote and contribute to their conservation in Portuguese continental waters.
With respect to the analysis of marine turtle strandings in continental Portugal, in the period 1978-2013, 57.1% of the recorded strandings corresponded to individuals of loggerhead turtle. Also, higher relative density values of loggerhead sea turtle strandings occur in the south coast of Portugal during spring and summer. The analysis of the causes of stranding and mortality revealed that interaction with fisheries was the main cause of stranding for this species. Regarding the feeding ecology of loggerhead sea turtles, we analyzed 95 digestive tracts of loggerhead turtles, stranded along the Portuguese continental coast, between 2010 and 2013. In the Portuguese continental coast, crustaceans were the main group of prey in the diet of loggerhead sea turtles, with the Henslow’s swimming crab (Polybius henslowii) and hermit crabs (Pagurus spp.) being the most important species. Sea turtles have recently been proposed at European level as good environmental status indicators (GES) under the MSFD (2008/56/EC), particularly with respect to monitoring descriptor D10 relating to changes in abundance of marine debris. In this context, out of the 95 loggerhead sea turtles whose digestive tracts were analyzed, 56 (59.0%) had marine litter in their tracts. Of these, more than half (56.8%) had ingested plastic items. It was also possible to deepen other aspects related with ocean pollution, such as the levels of inorganic elements in various tissues of loggerhead turtles. This study analyzed 38 loggerhead sea turtles and the results showed high concentrations of cadmium in kidney tissue (34.67±3.21µg/g), which may contribute to the deterioration of turtle health.
The present study, involving various aspects of the ecology of loggerhead sea turtles, is a pioneer in Portugal and provides an important basis for the development of future conservation efforts for this species in Portuguese continental waters. Overall, monitoring marine turtle strandings, the evolution of their diet, the presence of marine litter in their digestive tracts and their contamination levels may help to outline measures for their conservation within several European Directives frameworks, particularly in the context of Directive 2008/56/EC which establishes guidelines for marine environment policies in the European Union.
Keywords:
Caretta caretta,
strandings,
fisheries interactions,
Gut content analyses,
Anthropogenic threats,
marine litter,
Inorganic Elements
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:
Nicolau
LV,
Marçalo
A,
Ferreira
M,
Monteiro
S,
Sá
S,
Pereira
AT,
Santos
J,
Araújo
H,
Sequeira
M,
Vingada
J and
Eira
C
(2019). Influence of anthropogenic factors in the community of loggerhead sea turtles (Caretta caretta) in Portuguese continental waters.
Front. Mar. Sci.
Conference Abstract:
XX Iberian Symposium on Marine Biology Studies (SIEBM XX) .
doi: 10.3389/conf.fmars.2019.08.00031
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Received:
29 Apr 2019;
Published Online:
27 Sep 2019.
*
Correspondence:
Mx. Lidia V Nicolau, Sociedade Portuguesa de Vida Selvagem, Braga, Portugal, lvrnicolau@hotmail.com