Seagrass (Posidonia oceanica) monitoring in western Mediterranean: implications for management and conservation

In the Mediterranean Sea, the seagrass Posidonia oceanica plays a key ecological role, and is protected by a range of legislation. Standard Posidonia monitoring programmes generally focus on the plant at different spatial and short temporal scales, without considering the organisms dependent on the ecosystem. Passive acoustic monitoring (PAM) has a high potential to non-intrusively monitor biological activities and biodiversity at high temporal resolution, and to assess ecosystem health. This is particularly relevant considering that Posidonia meadows host numerous sound-producing fish species. In this study, bottommoored hydrophones were deployed in nine Western Mediterranean meadows covering a distance of more than 200 km to identify acoustic features potentially relevant to monitor this critical habitat. Among eight identified fish sound categories, we found a single type of sound (that we will refer to as /kwa/) dominating the soundscape of Posidonia meadows over a time span of 7 months. Compared to other low-frequency sounds, the /kwa/ presented unique characteristics that suggest it is produced by a fish via fast contracting muscles. The /kwa/ was the only sound detectable under anthropogenic noise conditions, and little affected by it. Cluster analyses performed on 13 acoustic features revealed a high degree of call diversity. /Kwa/ diversity, combined with its large-scale (all meadows), long-term (7 months) occurrence and low noise interference, make the /kwa/ a promising candidate for PAM of Posidonia meadows. Furthermore, variability in acoustic features suggests a central role of the /kwa/ in communication. Overall, this work sets the basis for establishing the relevance of the /kwa/ in monitoring P. oceanica meadows and developing PAM techniques for this critical habitat.

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“…Several long‐term projects currently monitor Posidonia meadows and follow anthropogenic impacts (Lopez y Royo et al. ; Holon et al. ,b).…”

Section: Introductionmentioning

confidence: 99%

‘Posidonia meadows calling’: a ubiquitous fish sound with monitoring potential

Iorio

Raick

Parmentier

et al. 2018

Remote Sens Ecol Conserv

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“…Additional sampling is necessary for each additional stratum. The number of sampling quadrats per sampling site used in practice to monitor shoot density in Posidonia rarely exceeds 36 (see also section 3.1, [ 29 ]). As shown in Fig 1 , this sampling effort cannot reliably detect a loss less than about 50%.…”

Section: Methods and Resultsmentioning

confidence: 99%

Error, Power, and Blind Sentinels: The Statistics of Seagrass Monitoring

et al. 2015

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We derive statistical properties of standard methods for monitoring of habitat cover worldwide, and criticize them in the context of mandated seagrass monitoring programs, as exemplified by Posidonia oceanica in the Mediterranean Sea. We report the novel result that cartographic methods with non-trivial classification errors are generally incapable of reliably detecting habitat cover losses less than about 30 to 50%, and the field labor required to increase their precision can be orders of magnitude higher than that required to estimate habitat loss directly in a field campaign. We derive a universal utility threshold of classification error in habitat maps that represents the minimum habitat map accuracy above which direct methods are superior. Widespread government reliance on blind-sentinel methods for monitoring seafloor can obscure the gradual and currently ongoing losses of benthic resources until the time has long passed for meaningful management intervention. We find two classes of methods with very high statistical power for detecting small habitat cover losses: 1) fixed-plot direct methods, which are over 100 times as efficient as direct random-plot methods in a variable habitat mosaic; and 2) remote methods with very low classification error such as geospatial underwater videography, which is an emerging, low-cost, non-destructive method for documenting small changes at millimeter visual resolution. General adoption of these methods and their further development will require a fundamental cultural change in conservation and management bodies towards the recognition and promotion of requirements of minimal statistical power and precision in the development of international goals for monitoring these valuable resources and the ecological services they provide.

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“…Efforts to conserve P. oceanica lie mostly in the establishment of marine protected areas, which seem to be insufficient to guarantee the protection of P. oceanica meadows (Montefalcone et al, 2009). Across the Mediterranean Sea, seagrass monitoring is extensive, but the adoption of different sampling designs and methods may result in erroneous comparisons (Lopez y Royo et al, 2010). Recently, the PMN has refined a standardised methodology for setting up P. oceanica monitoring systems, which has been applied in the Euro-Mediterranean region.…”

Section: Discussionmentioning

confidence: 99%

Seagrass recovery after fish farm relocation in the eastern Mediterranean

Kletou

Kleitou

Savva

et al. 2018

Marine Environmental Research

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Finfish aquaculture has damaged seagrass meadows worldwide as wastes from the farms can kill these habitat-forming plants. In Cyprus, the Mediterranean endemic Posidonia oceanica is at its upper thermal limits yet forms extensive meadows all around the island. Understanding this under-studied isolated population may be important for the long-term survival of the species given that the region is warming rapidly. When fish farming began around Cyprus in the mid-nineties, cages were moored above seagrass beds, but as production expanded they were moved into deeper water further away from the meadows. Here, we monitored the deepest edge of meadows near fish farms that had been moved into deeper waters as well as at a decommissioned farm site. Four P. oceanica monitoring systems were set up using methods developed by the Posidonia Monitoring Network. Seagrass % coverage, shoot density, % of plagiotropic rhizomes, shoot exposure, leaf morphometry, and sediment organic matter content and grain size were monitored at 11 fixed plots within each system, in 2012-2014 and in 2017. Expansion at the lower depth limit of seagrass meadows was recorded at all monitoring sites. Most other P. oceanica descriptors either did not change significantly or declined. Declines were most pronounced at a site that was far from mariculture activities but close to other anthropogenic pressures. The most important predictor affecting P. oceanica was depth. Monitoring using fixed plots allowed direct comparisons of descriptors over time, removes patchiness and intra-meadow variability increasing our understanding of seagrass dynamics and ecosystem integrity. It seems that moving fish farms away from P. oceanica has helped ensure meadow recovery at the deepest margins of their distribution, an important success story given that these meadows are at the upper thermal limits of the species.

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Seagrass (Posidonia oceanica) monitoring in western Mediterranean: implications for management and conservation

Cited by 19 publications

References 33 publications

‘Posidonia meadows calling’: a ubiquitous fish sound with monitoring potential

‘Posidonia meadows calling’: a ubiquitous fish sound with monitoring potential

Error, Power, and Blind Sentinels: The Statistics of Seagrass Monitoring

Seagrass recovery after fish farm relocation in the eastern Mediterranean

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