| Summary: | Cold-water corals such as Lophelia pertusa (= Desmophyllum pertusum, Linnaeus, 1758) with their reef-building capacity are true oases of life in the deep sea supporting a rich biodiversity. Today more than ever, deep-sea reefs worldwide are threatened by numerous natural and anthropogenic pressures. The Gulf of Cádiz acts as a transition zone and potential stepping stone between the cold Atlantic Ocean and the warm Mediterranean Sea, however, little is known about the distribution of L. pertusa in this area. Temperature has a major effect on Pelagic Larval Duration (PLD) and thereby may influence larval dispersal and connectivity patterns. In the light of global warming, shortened PLDs may negatively affect benthic sessile species like cold-water corals whose dispersal is limited to the larval stage. Biophysical models are cost-effective tools that allow to predict larval dispersal by combining existing knowledge on coral life-history traits, larval behaviour and ocean currents. The objectives of this thesis were to (1) describe the main larval dispersal pathways of L. pertusa and assess the potential connectivity between known colonies in this region, (2) identify potential new areas of coral occurrence, and (3) suggest “priority areas” for cold-water coral conservation. Larval dispersal was modelled via passive (i.e. no larvae behaviour) and active larvae (i.e. inclusion of ontogenetic vertical migration) as a function of temperature-varying PLD, larval swim speed and a temperature-avoiding behaviour of the larvae. The results showed high larval retention in the Gulf of Cádiz with dispersal into the Mediterranean Sea and along the western coast of the Iberian Peninsula, however this potential connectivity is limited when larvae disperse passively. Longer PLD generally facilitated larval dispersal and connectivity between coral sites. Conversely, slow vertical swim speed led to reduced dispersion and reduced connectivity between known locations with L. pertusa. Isolated colonies on offshore seamounts in the ...
|
|---|