Klima-aldaketaren eraginak euskal kostaldeko mendebaldeko sakonera handiko begetazio azpimarealean

Abstract

[eus] Euskal kostaldeko mareazpiko begetazioak aldaketa esanguratsuak jasan ditu azken hiru hamarkadetan. Aurretik egindako ikerketek jakinarazi dute aldaketa horiek klima-aldaketak eragindakoak direla. Ikerketa honen helburua inpaktu horri buruzko informazio gehiago lortzea da. Horretarako, sakonera handiko uretako fitobentosaren osaerari eta ugaritasunari buruzko balioespena egin da. 2014. urteko udan 7 trantsektu ezarri ziren, Kobaroneko muturretik Muskizeko muturreraino. Trantsektu horiek aurretik ikertuak izan ziren 1982 eta 2007 urteetan, eta laginketa suntsitzailea egin zen. Analisi estatistikoek aldaketa esanguratsuak erakusten dituzte sakoneko (9-11m) komunitateetan azken 32 urteetan. Uraren tenperaturaren emendioa eta eguzki-erradiazio altuagoa detektatutako aldaketen erantzuleak izan daitezke neurri batean. Pterosiphonia complanata espezie esziafiloaren gainbeherak eta Cystoseira baccata eta Aphanocladia stichidiosa espezieen ugaritzeak hipotesi hori azaltzen dute. Espero genuenaren kontra, Gelidium corneum espeziea, sakontasun gutxiko uretan gainbehera bortitza jasaten ari dena, ez da 9 metrotik beherako sakonerara lekualdatu. Hala ere, ezin da ziurtatu egungo ingurumeneko baldintzak optimoak ez direnik G. corneum espeziearen garapenerako 9-11 metroko sakoneretan. Migrazio bertikal hori ez gertatzearen arrazoi onargarriena C. baccata- rekiko lehiakortasuna dela dirudi. Bestalde, C. baccata hiru dimentsiotako habitatak eratzeko gai den tamaina handiko alga bat da, espezie askorentzat babesleku gisa diharduena. Ondorioz, haren hedapenak G. corneum-ek sakonera txikiagoetan betetzen zuen funtzioa ordezka lezake neurri batean.

[en] The subtidal vegetation of the Basque coast has suffered significant changes in the past three decades. Previous studies have shown that these changes are due to the impact of climate change. The present study aims to provide more information concerning the impact, for which, makes an assessment of the composition and abundance of phytobenthos in deep waters (10- 11m). For this purpose, 7 transects were established from Punta Muskiz to Punta Kobaron in summer 2014, which were previously analyzed in 1982 and 2007, and a destructive sampling was performed. Statistical analyzes revealed a significant change in the communities in the past 32 years. Factors such as rising water temperatures and a greater availability of light could be partly responsible for the detected changes, as suggested by the decline of sciaphilous species Pterosiphonia complanata and the increases in Cystoseira baccata and Aphanocladia stichidiosa. Contrary to our predictions, Gelidium corneum, which is suffering a decline in shallow waters due to excessive irradiance, has not shifted to depths below the 9 m deep. Although it cannot be ruled out that the current environmental conditions at that depth are not optimal for the development of G. corneum, competitive exclusion with C. baccata it is probably the most plausible explanation for the absence of vertical migration of G. corneum. Moreover, since C. baccata is a large-sized macrophyte capable of generating a three- dimensional habitat for numerous species, its expansion could replace, at least partially, the function developed by G. corneum in shallower waters.