Abstract
Even during the current biodiversity crisis, reports on population collapses of highly abundant, non-harvested marine species were rare until very recently. This is starting to change, especially at the warm edge of species’ distributions where populations are more vulnerable to stress. The Levant basin is the southeastern edge of distribution of most Mediterranean species. Coastal water conditions are naturally extreme, and are fast warming, making it a potential hotspot for species collapses. Using multiple data sources, I found strong evidence for major, sustained, population collapses of two urchins, one large predatory gastropod and a reef-building gastropod. Furthermore, of 59 molluscan species once-described in the taxonomic literature as common on Levant reefs, 38 were not found in the present-day surveys, and there was a total domination of non-indigenous species in molluscan assemblages. Temperature trends indicate an exceptional warming of the coastal waters in the past three decades. Though speculative at this stage, the fast rise in SST may have helped pushing these invertebrates beyond their physiological tolerance limits leading to population collapses and possible extirpations. If so, these collapses may indicate the initiation of a multi-species range contraction at the Mediterranean southeastern edge that may spread westward with additional warming.
Highlights
Species collapses or extirpations in the region
In the large whelk Stramonita haemastoma, significant signs of rapid decline were already evident in the late 1990’s when populations were still abundant but no recruitment of young was seen for five years[31], leading to a total collapse, demonstrated here by its complete absence in the last seven years (2009–2015) in Achziv, where it was most abundant in the 1990 s (Fig. 2a)
Given the evidence shown in this study for major population collapses of dozens of invertebrates and one algae, it is highly probable that many other taxa from even less-studied groups have seriously declined in the southern Levant—unnoticed
Summary
Species collapses or extirpations in the region ( some population declines were suggested to be related to exclusion by invaders ref. 19). Such sources can include sporadic surveys that consist of one or a few data points (see for example refs 23,24), taxonomic information with some reference to relative abundance, even if descriptive, and museum records[8,25], as well as local knowledge that can be assessed with questionnaires targeting naturalists and professionals (fisherman, divers and academics) alike[26,27,28] Using this approach, in this study, I compare data from recent (2009–2015) comprehensive rocky intertidal and subtidal biodiversity surveys (thousands of quadrats and hundreds of dives) on the Israeli coast (Fig. 1), as well as three “reference” sites further west surveyed in 2013 and 2014, to (1) data from past sporadic surveys (conducted in the 1970 s and 1990 s) of four once highly-abundant, ecologically-important invertebrate species that are not commercially or artisanally harvested, (2) abundance categories in a detailed Levantine mollusca taxonomic publication based on past semi-quantitative surveys conducted between the 1967–7729,30, (3) malacological museum records, (4) survey of local knowledge on one taxon (urchins) conducted in 2015. I compiled remote-sensing and nearshore in-situ temperature data to verify the recent warming trends of the southeastern Levant coastal waters
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
