Gibraltar in winter-spring, followed by growth of young thalli if the SST remains
relatively low, which is macroecologically affected by the NAO. However,
the survival of the thalli could be also favoured by the effects of the NAO over the
Atlantic Jet (AJ). The position of the AJ coming from the Atlantic Ocean into the
Mediterranean Sea is variable (Vargas-Yáñez et al. 2002; Macías et al. 2016) with a
north-south migration pattern (Sarhan et al. 2000). The speed of the incoming AJ
increases at low pressure over the western Mediterranean (Timplis and Josey 2001;
García-Lafuente et al. 2002). Increasing velocity enhances the Coriolis force and
separates the AJ from the Spanish coast, facilitating the upwelling of cold Mediterranean water (14
C to 17
C) at the Spanish coast and, consequently, allowing the
survival of F. guiryi thalli. A similar pattern was suggested by Lourenço et al. (2016)
in other locations where this species appears associated with an upwelling. In
contrast, under negative NAO index, the AJ velocity might decrease and the Western
Alboran gyre, characterized by warmer water, migrates northward and may reach the
coast at Punta Calaburras. This increases the probability of short-term periods of
very warm water (up to 22
C) that hinder survival of F. guiryi thalli under negative
NAO index.
The occurrence of harmful algal blooms (HABs) is also a function of the physical
and environmental controls acting on the HAB species and, for this reason, it must be
considered as a macroecological phenomenon. Recent studies suggested that the
occurrence in the Alboran Sea of the toxic dinoflagellates Gymnodinium catenatum
(producer of the PSP toxin) could be modulated by the NAO of the previous
4 months, while the appearance of Dinophysis acuminata (producer of the DSP)
could be linked to the AO from 3 months before. This implies a relationship between
interannual and multidecadal-scale variability of atmospheric oscillations and HABs
similar to that suggested for the northeast Atlantic (Edwards et al. 2006; Hinder et al.
2011).
This macroecological relationship between Alboran populations and
macroclimate leads to thinking that climate warming and, more generally, global
change is affecting both species composition and ecology. Future scenarios contemplating an increase of extreme values in atmospheric cycles due to climatic change
have been proposed (Vicente-Serrano et al. 2011). It could therefore be hypothesized, for example, that toxic algal events will increase in association with increased
extreme values of NAO and AO indices, taking into account the significant
favourabilities already demonstrated for HAB in the marine systems of SW Europe.
In fact, it has been proposed that HAB caused by dinoflagellates (Hallegraeff 2010;
Philipparta et al. 2011; Fu et al. 2012) will increase as a result of climate change.
Recent nesting events of loggerhead sea turtle (Caretta caretta) are also occurring
periodically on the Spanish Mediterranean coast since the first reported nesting in
Vera, northern Gata cape, in 2001 (Tomas et al. 2002) and the recent nesting in
northern Alboran (Báez et al. 2020), in what seems to be an increasing trend in
nesting of this species in this basin. This change in the nesting behaviour of this
species seems to be related to changes in climate and beaches temperature. Clearly,
more studies must be carried out on this matter. On the other hand, the effect of
overfishing must also be considered, as it destroys funds and alters the structure of
11 Biogeographical and Macroecological Context of the Alboran Sea
447
relatively low, which is macroecologically affected by the NAO. However,
the survival of the thalli could be also favoured by the effects of the NAO over the
Atlantic Jet (AJ). The position of the AJ coming from the Atlantic Ocean into the
Mediterranean Sea is variable (Vargas-Yáñez et al. 2002; Macías et al. 2016) with a
north-south migration pattern (Sarhan et al. 2000). The speed of the incoming AJ
increases at low pressure over the western Mediterranean (Timplis and Josey 2001;
García-Lafuente et al. 2002). Increasing velocity enhances the Coriolis force and
separates the AJ from the Spanish coast, facilitating the upwelling of cold Mediterranean water (14
C to 17
C) at the Spanish coast and, consequently, allowing the
survival of F. guiryi thalli. A similar pattern was suggested by Lourenço et al. (2016)
in other locations where this species appears associated with an upwelling. In
contrast, under negative NAO index, the AJ velocity might decrease and the Western
Alboran gyre, characterized by warmer water, migrates northward and may reach the
coast at Punta Calaburras. This increases the probability of short-term periods of
very warm water (up to 22
C) that hinder survival of F. guiryi thalli under negative
NAO index.
The occurrence of harmful algal blooms (HABs) is also a function of the physical
and environmental controls acting on the HAB species and, for this reason, it must be
considered as a macroecological phenomenon. Recent studies suggested that the
occurrence in the Alboran Sea of the toxic dinoflagellates Gymnodinium catenatum
(producer of the PSP toxin) could be modulated by the NAO of the previous
4 months, while the appearance of Dinophysis acuminata (producer of the DSP)
could be linked to the AO from 3 months before. This implies a relationship between
interannual and multidecadal-scale variability of atmospheric oscillations and HABs
similar to that suggested for the northeast Atlantic (Edwards et al. 2006; Hinder et al.
2011).
This macroecological relationship between Alboran populations and
macroclimate leads to thinking that climate warming and, more generally, global
change is affecting both species composition and ecology. Future scenarios contemplating an increase of extreme values in atmospheric cycles due to climatic change
have been proposed (Vicente-Serrano et al. 2011). It could therefore be hypothesized, for example, that toxic algal events will increase in association with increased
extreme values of NAO and AO indices, taking into account the significant
favourabilities already demonstrated for HAB in the marine systems of SW Europe.
In fact, it has been proposed that HAB caused by dinoflagellates (Hallegraeff 2010;
Philipparta et al. 2011; Fu et al. 2012) will increase as a result of climate change.
Recent nesting events of loggerhead sea turtle (Caretta caretta) are also occurring
periodically on the Spanish Mediterranean coast since the first reported nesting in
Vera, northern Gata cape, in 2001 (Tomas et al. 2002) and the recent nesting in
northern Alboran (Báez et al. 2020), in what seems to be an increasing trend in
nesting of this species in this basin. This change in the nesting behaviour of this
species seems to be related to changes in climate and beaches temperature. Clearly,
more studies must be carried out on this matter. On the other hand, the effect of
overfishing must also be considered, as it destroys funds and alters the structure of
11 Biogeographical and Macroecological Context of the Alboran Sea
447