Abstract
Mediterranean coasts are affected by multiple mounting pressures. In Cyprus, marine fish farming has grown rapidly in the past decade and is concentrated in the west side of Vasiliko Bay. The east coast of this bay has ports, a power station, a desalination unit, a cement factory, a major new oil terminal, and gas storage facilities. The bay is earmarked to create the largest hydrocarbon processing, storing, and transport facility in the region. Here, we assess the status of Posidonia oceanica habitat in an understudied region at the upper thermal, and eastern limit, of this Mediterranean endemic seagrass. An extensive ancient seagrass meadow was revealed, covering about 200 ha across 10 km of coastline, over soft substrata at ca 10–30 m depth, and over hard substrata at ca 0–6 m depth. Seagrass shoot density and leaf surface area decreased, both with increasing depth and with proximity to industrial developments; part of the meadow had been destroyed by dredging to build a jetty. Close to fish farms the seagrass had higher epiphytic biomass as well as lower leaf number, mass, and surface area, all of which indicate adverse effects of eutrophication and increased turbidity. Despite these multiple stressors, most of the meadow was in good ecological status, with some of the highest shoot densities ever reported. Furthermore, iconic species like sea turtles, monk seals, and dolphins were seen during sampling. Posidonia oceanica meadows off Cyprus are among the most valuable in the Mediterranean due to their tolerance of high seawater temperatures. Managers of future coastal developments in the region will need to adhere to European legislation and international conventions designed to secure the socioeconomic benefits of seagrass beds.
Highlights
Seagrass meadows provide valuable ecosystem services but are being lost at 7% year−1 globally [1], with water quality and other stressors placing seagrass meadows among the most threatened ecosystems on Earth [2]
We review whether P. oceanica descriptors are different compared to cooler and less oligotrophic sites around the Mediterranean
The reference conditions used in the calculation of the ecological status class (ESC) scores were: (i) those suggested by Lopez et al [29] for BiPo and applied in the central and western Mediterranean, (ii) the reference values set by the national authority of Cyprus for PREI, following the intercalibration MedGIG exercise, and (iii) the reference conditions adapted for the area of study and the time of sampling, set for the shoot density and foliar surface shoot−1 as the average of the three highest values measured during the survey [34]
Summary
Seagrass meadows provide valuable ecosystem services but are being lost at 7% year−1 globally [1], with water quality and other stressors placing seagrass meadows among the most threatened ecosystems on Earth [2]. Posidonia oceanica can withstand seawater temperature variations, many contaminants, and alien species invasion, but it is highly sensitive to salinity fluctuations, turbidity and increased sedimentation, anchoring, and trawling [21]. Habitat loss of this species is considered irreversible on human time-scales [22], because even if optimal conditions return, impacted areas take centuries to be recolonised [23,24]. The meadows cover an estimated area of 9040 ha in the 30% of the Cyprus coastline that has been surveyed [7] These P. oceanica meadows seem to be genetically isolated from those in the western and central Mediterranean [26,27,28]. We review whether P. oceanica descriptors are different compared to cooler and less oligotrophic sites around the Mediterranean
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