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Benthic foraminifera as bioindicators of anthropogenic impacts in two north African lagoons: January 20, Corrected manuscript received: May 1, Manuscript accepted: Numerous investigations have used the foraminiferal assemblages or species as bioindicators.

This paper tests the responses of these microorganisms to different environmental changes heavy metal foraminieros, treatment stations, artificial inlets, agricultural and urban sewages and compares them to those observed previously on ostracod assemblages.

Foraminifera are more tolerant to these changes, while ostracods present a more specialized foraminifdros. These ecosystems are widely distributed along the peri-Mediterranean coasts, covering approximatelyha at present Trabelsi et al.

Both lagoons are subjected to different environmental impacts derived from public treatment stations, mining activities, agricultural residues or industrial wastes Figure 1.

Foraminifera are usually included between the most promising palaeo- environmental bioindicators in recent and Holocene coastal areas e. Effects of anthropogenic impacts on foraminiferal assemblages have been widely studied see Alve, ; Yanko et al.

In addition, changes on foraminiferal diversity, density or assemblages and even morphological abnormalities have been observed in different lagoons with heavy metal pollution or eutrophication e.

Luciani, ; Buosi et forwminiferos.

Foraminíferos bentónicos actuales (Marginopora vertebralis… | Flickr

The aim of this study is to describe the impacts of anthropogenic inputs on foraminiferal communities, waters and sediments foraminiferoe both Nador and El Melah lagoons. Foraminiferal response to environmental stress is compared with the response of ostracod populations in order to determine the effectiveness of both groups as environmental proxies.

The Nador lagoon is the second largest lagoon complex of northern Africa km 2 foraminifreos the broadest paralic environment of Morocco. This lagoon is protected by a NW-SE elongated spit 25 km lengthonly interrupted by an artificial inlet limited by two jetties that comunicates it with the Mediterranean Formainiferos Figure 1a.

Most of the areas present water depths between 3 and 7 m, with an internal hydrodynamics dominated by the marine waters passing through the artificial inlet.

Tidal regime is microtidal 0. Salinity range is typical of marine waters Dissolved oxygen contents are very variable 3. This lagoon is subjected to an increasing anthropogenic pressure owing to the economic activities in the adjacent areas: Kariet Arkmane; sample N4 drain their fecal waters directly into the lagoon foraminiferoz any previous treatment. This lagoon presents an artificial connection 8 m long with the Gulf of Tunis, crossing a littoral dune strand Figure 1b.

Four main geo-morphologic units may be distinguished: Saliniy ranges from 5. Waters are mostly alkaline pH 7. Several anthropogenic inputs cause important environmental changes: Four sites were selected from each lagoon to test the impact of different anthropogenic inputs Figure 1 on the foraminiferal populations. In each site, three duplicated sub-samples were obtained for water, sediment and microfaunal analyses.


Water sub-samples were subjected to the following procedures in the Surface Geochemical Centre Strasbourg, France: Sediments were collected manually from the upper 2 cm and wet sieved in order to establish the grain-size distribution. Additional sub-samples were selected for the analysis of the foraminiferal record present in this upper layer Table 1c. In each sample, g dry weight were slowly passed through a 63 Lm sieve. The samples were stained with Rose Bengal in order to recognize the live individuals.

Up to individuals were picked in the final residues, if possible. More than specimens were studied to determine the percentages of the different species. Finally, both density number of individuals per gram and diversity number of species of each sample were calculated.

Consequently, the use of total assemblage live plus dead specimens was preferred as an indicator of average environmental conditions for documenting of the foraminiferal response to anthropogenic inputs e. Results were compared with the ostracod assemblages obtained by Ruiz et al.

Foraminiferal assemblages show variable responses to different anthropogenic related activities. In the Nador lagoon, the most extreme of them was observed in highly polluted sediments by heavy metals collected near an old iron mine Table 1c: This species is a bioindicator species of metal pollution in salt lakes of Turkey Barut et al. Under these conditions, shallow marine assemblages of miliolids Quiqueloculina spp, Sinuloculina spp. Diversity is clearly lower near the artificial jetties of Nador lagoon four speciesa very unstable area owing to the dredging of the bottom sediments and the permanent traffic of fishing boats in relation to the quieter artificial inlet of El Melah lagoon Table 1c: This hydrodynamic stress is an unfavourable factor for the development of these microorganisms Ruiz et al.

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A high percentage of miliolids show evidences of transport fractures, loss of the last chamberwhich confirms the unstability of this area. Wastes derived from treatment stations cause different response in both lagoons.

Nutrient contents increase slightly near the Nador treatment station Table 1a: These variations were observed, to a lesser extent, in some old saltworks of El Melah lagoon sample E3with very high phosphate contents. A small increase in nutrients can foramoniferos beneficial for foraminifera, although a high nutrification may have negative effects on them Osawa et al.

Low salinities measured near the treatment station of El Melah lagoon sample E2: The main effect is a marked decrease in the foraminiferal diversity and the dominance of brackish species e. Bentoniccos, dilution by fresh water causes a strong disturbance on the foraminiferal associations, as noted in other semi-arid lagoons Hariri, The eastern borders of both lagoons samples N4 and E4 present foraminiferal assemblages similar to those observed in foraminiferros sediments e.

In Nador lagoon, small agricultural wastes and urban sewages do not harm significantly benthic foraminifera, as pointed Samir in different lagoons of Egypt. Nevertheless, the density of E4 El Melah lagoon is much lower, coinciding with low bnetonicos contents, an algal covert and a low tidal renewal. Ostracoda as environmental tracers: A comparison of these results with those obtained by Ruiz et al.


High levels of trace metals cause the disappearance of ostracods and the exclusive presence of tolerant species of foraminifera, a response observed in other areas subjected to acid mine drainage processes and recent industrial pollution Ruiz et al. In addition, our data confirms the role of Nonion depressulum to bio-indicator of stressing conditions State University System of Florida, The natural evolution of these semi-arid lagoons involves a natural process of closure, with a final transition to bentoncios sabkha scenario.

Artificial inlets cause the foraminiferso of both marine sediments and species into the lagoons and a partial erosion of the adjacent bottom areas due to the channeling of the tidal currents. These conditions are unfavourable for both foraminifera bentinicos ostracods e. The main effect of the Nador waste treatment station is the presence of low O2 dissolved contents 3.

Foraminiferal assemblages are dominated by stress-tolerant genera Ammonia, Nonionwhereas a high proportion of the ostracod faunas are represented by opportunistic species mainly loxocon-chids tolerant to hypoxic conditions Alvarez-Zarikian et al. Salinity is a major factor regulating ostracod community structure and the response of these crustaceans is the appearance of steno-haline species limited to freshwater to low brackish water ranges e.

Ilyocypris gibba Ramdohr, hentonicos, Heteroris salina Brady, This impact was also noted on foraminiferal populations, but they foraminiefros constituted mainly by euryhaline, sometimes opportunistic species e.

Foraminifera do not show a specific response to these low-level environmental impacts, whereas both density and diversity of ostracods decrease.

Rivista Italiana di Paleontologia e Stratigrafia (Research In Paleontology and Stratigraphy)

The presence of low tidal renewal and a algar covert cause oxygen depletion, with low foraminiferal density and bentoincos. The database of anthropogenic inputs provided by the COLASU project permits to establish the utility foraminiferoos benthic foraminifera as bioindicators. Some genera are highly tolerant to eutrophication e. Ostracods show a different response, with a disappearance under high pollution conditions, the presence of opportunistic, low-oxygen tolerant species in eutrophic areas or stronger changes of associations linked to salinity variations inlets, treatment stations.

Therefore, it is possible to establish an approximation of the degree of environmental impact of these changes for these lagoons: Hariri for critical, helpful and constructive reviews of the manuscript. The Coastal Society, Journal of Foraminiferal Research, 25, Environmental Pollution, Geophysical Research Abstracts, 9, Estuarine, Coastal and Shelf Science, 66, Bilan d’automne 76 and d’hiver Present Environment and Sustainable Development, 4, Carnegie Institution of Washington Publications, A review of Italian research over the last three decades: Marine Sciences, 19, University of Rabat, Morocco, Ph.

Marine Pollution Bulletin, 60, Journal of Arid Environments, 69, Journal of African Earth Sciences, 44, Environmental Research, Marine Pollution Bulletin, 56, Journal of Foraminiferal Research, 30, Estuarine, Coastal and Shelf Science, 61, Journal of Foramiferal Research, 38, Kluwer Academic Publisher, Dordrecht, pp.

An approach A comparison of these results with those obtained by Ruiz et al.