Assessment of the environmental health status of the Marchica lagoon (Morocco, Mediterranean) using Cymodocea nodosa meadows and its associated macrofauna: preliminary results
Reda El KamchaOussama BououarourLoubna BoutaharZineb El FatouaniAyoub El AdnaniBendahhou ZourarahYassine Ramzi SghaierAbdelaziz BenhoussaHocein Bazaïri
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The Marchica lagoon is the single lagoon on the Mediterranean coast of Morocco. Beside its ecological and socio-economic values, the lagoon is under pressure of a complex mixture of human-mediated stressors (urbanization, pollution, overfishing, tourism, etc.). Nowadays, many institutional efforts have been undertaken to establish a sustainable management plan of the lagoon in the context of an Integrated Coastal Zone Management (ICZM) approach. Thus, understanding how these stressors impact upon ecological status and ecosystem services is a sound step for any efficient integral management. Based on sampling performed on June 2014, the present work aimed at assessing the ecological quality status (ES) of the northern part of the lagoon using Cymodocea nodosa (Ucria) Ascherson meadows and benthic macrofauna. 16 stations (11 with C. nodosa and 5 on bare sediment) were sampled using a Van Veen grab. Preliminary results showed differences between stations. Shoots biomass fluctuated between 8.02 and 61.2 g dw m-2 while the roots-rhizomes biomass oscillated between 10.8 and 235.5 g dw m-2. The root-rhizome and leaf biomass ratio revealed high values (up to 10.8) in the central sector suggesting a potential nutrient enrichment.Benthic macrofauna revealed the presence of 90 species belonging to six zoological groups and dominated by crustaceans, molluscs and polychaetes. The assessment of the ecological quality status, based on benthic macrofauna, was evaluated using Biotic Indices (AMBI, M-AMBI, Benthix, BITS). The results showed partial agreement between single index-derived ES and underlined the dependency of these biotic indices on the habitat characteristics, on the one hand, and the necessity to define specific reference conditions to the Marchica lagoon.Keywords:
Biotic index
Posidonia oceanica
Posidonia oceanica
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Posidonia oceanica
Paracentrotus lividus
Epiphyte
Diplodus
Zostera marina
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Mediterranean seagrass Posidonia oceanica is used as a common biological indicator in the monitoring programmes of the Water Framework Directive (WFD) due to its structural and functional features providing information about the status of coastal ecosystems. In this respect synthetic seascape ecological indices using P. oceanica: the Conservation Index (CI), the Substitution Index (SI), the Phase Shift Index (PSI) and the Patchiness Index (PI) provide supplementary data on the meadow status and on the pressures affecting the meadows besides evaluating the water quality. However, these indices have not been adopted by the European Union Water Framework Directive (WFD). This survey is, therefore focused on the qualification of the status of coastal ecosystems in the North Aegean Sea with an integrated approach based on the synthetic (the CI, the SI, the PSI and the PI) and biotic indices (Biotic Index of Posidonia and Ecosystem Based Quality Index) of P. oceanica. Measurements of several parameters are conducted in four sites (2 natural, 2 anthropized) in Gökçeada (North Aegean). The preliminary results confirm the efficiency of synthetic and biotic indices to evaluate the ecosystem status in relation with anthropogenic pressures at a local extent. The mean value of the CI corresponds to a "good" status, while the value of the BiPo Index corresponds to a "moderate" and the value of the EBQI corresponds to a "poor" status for Gökçeada. Maximum values of the synthetic and biotic indices are recorded in natural sites. On the contrary, minimum values are recorded in anthropized sites close to marine-based activities. In addition, an early stage of a phase shift (PSI < 0.25) is recorded due to a low substitution with Caulerpa cylindracea spread around fragmented meadows and dead matte areas. Also, relations (p < 0.05) between the scores of the Land Uses Simplified Index (LUSI) and combined synthetic and biotic indices of P. oceanica, verified the negative impacts of anthropogenic pressures on the benthic ecosystems of the North Aegean Sea where the data is deficient.
Posidonia oceanica
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Water Framework Directive
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Since the seagrass Posidonia oceanica is highly sensitive to environmental changes, a monitoring of the physiognomy, phenology and lepidochronology of the meadows was conducted during 2015-2020 at Tremiti Islands Marine Protected Area (Adriatic Sea). The meadow resulted stressed where anthropogenic disturbances occurred, while the implementation of proper management measures proved to trigger the recovery of the habitat. Our results underlined the importance of P. oceanica as a biological indicator to monitor human activities at local scale.
Posidonia oceanica
Marine protected area
Potamogetonaceae
Marine habitats
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Posidonia oceanica (Linnaeus) Delile 1813 is an endemic and the most widespread seagrass species of the
Mediterranean Sea. Seagrass meadows are one of the most productive ecosystems on Earth, providing habitat to
numerous organisms. Therefore, mapping of seagrass meadows is of crucial importance for conservation and
coastal management purposes. Here we present an integrated geographic information system approach with
SCUBA diving, providing a cost effective method to monitor seagrass beds at shallow coastal habitats. In this
case study P. oceanica meadows were mapped in Ufakdere region of Kaş (Antalya) coastal area between April
– September 2015. A total of 25000 m2
are were screened to create seagrass coverage maps. Results indicate that
P. oceanica meadows cover 21200 m2
and we estimated that 520 m2 of this area is highly damaged. This
integrated approach provided one of the most detailed small-scale Posidonia mapping in Turkey and this time
and cost effective methodology can be applied to any seagrass meadow with great ease to increase our knowledge
on this important habitat.
Posidonia oceanica
Scuba diving
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Marine ecosystem
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Benthic macroinvertebrate samples were taken seasonally from October 2006 to April 2008 except winter seasons with the aim of evaluate macroinvertebrate fauna and water quality of Suleymanli Lake. In total, 61 benthic macroinvertebrate taxa were found and 40 of them are new records for the lake. Chandler Score and Shannon-Weiner Diversity Index provided more compatible data than Revised Biological Monitor- ing Working Party, Extended Trent Biotic Index and Belgian Biotic Index with physical-chemical results. Also, Principle Component Analysis was carried out to establish associations between benthic macroin- vertebrates and environment variables. In our study, the lake water quality was determined as moderately polluted. Obtained environmental variables from water samples showed that the temperature, dissolved oxygen, pH, total dissolved solids and electrical conductivity are the most important parameters in ex- plaining the macroinvertebrate community variation in the lake.
Biotic index
Diversity index
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Seagrass meadows are vital coastal habitats that support a wide array of species and provide numerous ecosystem services. The area of seagrass meadow has declined significantly, at a rate of about 5% per year, since 1980. Emerging techniques for seagrass research has the potential to provide new insights to fill knowledge gaps and improve our understanding of seagrass ecological function and ecosystem services. This improved understanding will help us to inform policy makers about protection measures. Using Posidonia oceanica dominated habitats as a case study, this thesis assesses emerging techniques for mapping seagrass habitats, monitoring biodiversity with seagrass habitats and assessing microplastic pollution loads within seagrass sediments.
Kayak-borne down-scan sonar is shown to provide an accurate and cost-effective method for mapping the distribution of seagrass meadows. Sonar-derived data suggested current estimates of seagrass extent in the Aegean, based on analysis of satellite imagery, may contain considerable inaccuracies particularly in areas of complex bathymetry. It is suggested that kayak-borne sonar mapping can provide accurate reference data for larger scale satellite mapping, delivering benefits in terms of our ability to survey seagrass distribution and monitor temporal changes in extent and health.
Environmental DNA is proven to be an effective tool for the non invasive detection of, Pinna nobilis, a culturally important yet Critically Endangered bivalve species associated with P. oceanica habitats. The technique developed in this study is capable of detecting concentrations of DNA as low as 5.50 x 10-10 ng µl-1 from sea water samples. This technique can be used at different spatial scales dependent on the season, allowing eDNA to be a sensitive and precise tool in locating and identifying a key species inhabiting seagrass meadows.
A fine-scale analysis of microplastic distribution within the sediment under a seagrass meadow using recently developed Sediment Microplastic Isolation techniques, indicated that seagrass did not influence the deposition of microplastics to sediment at a semi isolated bay. Microplastics were recovered at relatively low densities across the entire study area. Analysis of sediment patterns suggested that most sediment input was from terrestrial sources immediately adjacent to the seagrass bed and, therefore, that seagrass beds that are closer to terrestrial sources of microplastic pollution are likely to show much greater microplastic loadings.
It is concluded that, emerging techniques such as down-scan sonar, eDNA and microplastic extraction can provide novel insights into the distribution and ecological functioning of seagrass habitats. These insights provide avenues for the development of existing monitoring methods and for conservation policies.
Posidonia oceanica
Marine habitats
Marine protected area
Marine ecosystem
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