Growing coastal tourism: Can biomonitoring provide insights into the health of coastal ecosystems?

Coastal tourism's surge raises concerns for Morocco's Agadir marine environment, notably with Taghazout Bay's impact. Our study assesses Taghazout's health, employing a comprehensive approach. Our study evaluates Taghazout's health, adopting a comprehensive approach covering physicochemical, microbiological aspects, macrobenthic fauna, metal pollution, and biomarkers in D. trunculus mollusks. Seawater quality aligns with Moroccan standards, indicating good bathing water. The intertidal zone hosts ten species, dominated by D. trunculus. Biomarker responses in D. trunculus suggest chemical stress. Land-use maps expose significant changes driven by the Taghazout Bay project, impacting approximately 37.99 % of the landscape. Construction activities notably encroached upon the Arganeraie and the coastal zone, creating a stark contrast from 2003. These findings form a crucial database for future studies, contributing significantly to environmental management and sustainable development, aiding informed decision-making and effective coastal ecosystem preservation strategies.

Influence of wastewater treatment on the reproduction and growth of Mytilus galloprovincialis in Agadir's central Atlantic marine ecosystem, South Morocco.

Mytilus galloprovincialis is common in Morocco's Anza-Taghazout coast, previously polluted by wastewater. Since treatment plants were installed in 2016, no study examined the mussels' reproduction. Our study assessed how wastewater treatment affects the reproduction and growth of the M. galloprovincialis mussel on Moroccan coasts, particularly in the Anza-Taghazout area. We aimed to clarify the impacts of treated effluents on this vital invertebrate. This research explored their reproductive parameters, with samples taken from 2017 to 2018 at Anza, Aourir, and Imouran. Results show all gametic stages with three spawning periods. The gonadal index exceeds 1.4 at all sites, indicating a short resting phase. The sex ratio is balanced in Aourir and Imouran, but Anza has more males. The length-weight relationship showed the b value of 1.56 (R2 = 0.32); 1.71 (R2 = 0.35), and 1.70 (R2 = 0.26) for Anza, Aourir, and Imouran respectively. This suggests a slight negative allometric relationship. The condition index showed a progressive trend, and M. galloprovincialis improved due to enhanced environmental quality after treatment.

The impact of climate change and pollution on trematode-bivalve dynamics.

Coastal ecosystems and their marine populations are increasingly threatened by global environmental changes. Bivalves have emerged as crucial bioindicators within these ecosystems, offering valuable insights into biodiversity and overall ecosystem health. In particular, bivalves serve as hosts to trematode parasites, making them a focal point of study. Trematodes, with their life cycles intricately linked to external factors, provide excellent indicators of environmental changes and exhibit a unique ability to accumulate pollutants beyond ambient levels. Thus, they act as living sentinels, reflecting the ecological condition of their habitats. This paper presents a comprehensive review of recent research on the use of bivalve species as hosts for trematodes, examining the interactions between these organisms. The study also investigates the combined impact of trematode infections and other pollutants on bivalve molluscs. Trematode infections have multifaceted consequences for bivalve species, influencing various aspects of their physiology and behavior, including population-wide mortality. Furthermore, the coexistence of trematode infections and other sources of pollution compromises host resistance, disrupts parasite transmission, and reduces the abundance of intermediate hosts for complex-living parasites. The accumulation process of these parasites is influenced not only by external factors but also by host physiology. Consequently, the implications of climate change and environmental factors, such as temperature, salinity, and ocean acidification, are critical considerations. In summary, the intricate relationship between bivalves, trematode parasites, and their surrounding environment provides valuable insights into the health and sustainability of coastal ecosystems. A comprehensive understanding of these interactions, along with the influence of climate change and environmental parameters, is essential for effective management and conservation strategies aimed at preserving these delicate ecosystems and the diverse array of species that rely on them.

Do the individual and population-level traits of Donax trunculus reflect the effects of metal contamination in aquatic environments?

Heavy metals are considered a major threat to aquatic ecosystems, due to their ability to penetrate and accumulate through the food chain, putting marine organisms and the ecosystem at risk. This research presents a case study of the Taghazout coast, located in the central Atlantic of Morocco, which has become the focal point of various development projects, including the Taghazout Bay tourist resort. The study aimed to gain a deeper understanding of the harmful effects of these metals on the reproductive cycle and population dynamics of the bivalve Donax trunculus. The assessment of cadmium (Cd), lead (Pb), and copper (Cu) levels in D. trunculus bivalves and sediment at the research location provides evidence of exposure to these metal sources by these bivalves. The analysis of the reproductive cycle revealed a balanced sex ratio of males to females. The Sexual Maturity Index (SMI) and Condition Index (CI) of the bivalves were found to be significantly influenced by trace elements Pb and Cu, as well as environmental factors like temperature, dissolved oxygen, and salinity. The maturity stages of the gonads were classified into five stages: undifferentiated, developing, mature, spawning, and spent. Two spawning periods were observed aligning with the population dynamics study that identified a bimodal recruitment (early autumn and spring) in D. trunculus. The population was found to have 11 size cohorts, with a maximum length of 37.96 cm, a yearly growth rate of 1.93 cm, and a short lifespan of 1.5 years. The high mortality rate of 3.30 per year was attributed to the presence of trace elements in Taghazout coast. These findings shed light on heavy metal's impact on the population of D. trunculus, revealing that a sole emphasis on its physiological or cellular effects may overlook its larger impact.

Assessment of heavy metal contamination and ecological risk in Morocco's marine and estuarine ecosystems through a combined analysis of surface sediment and bioindicator species: Donax trunculus and Scrobicularia plana.

Morocco is one of the most affected regions by heavy metal pollution worldwide. In this study, two ecosystems in Agadir Bay, southern Morocco, were studied seasonally, using surface sediment and bivalve species. The concentrations of Cu, Pb and Cd were determined using the Shimadzu AAS 7000 flame atomic absorption spectrophotometer method. Our results marked average levels corresponding to an unpolluted sediment with a low contamination degree, low ecological risk associated with metal contamination, and levels that did not exceed the thresholds set by EC, USEPA, INERIS and INRH, except for Pb in tourist beach. The principal component analysis findings revealed a positive correlation in the bioaccumulation between the two compartments, with an influence of abiotic parameters. Thus, to better manage environmental pollution in these ecosystems, authorities must implement waste treatment strategies in the surrounding harbor and tourist complexes and prohibit the use of these toxic metals in the coastal areas.

Integrated biomarker responses and metal contamination survey in the wedge clam Donax trunculus from the Atlantic coast of Morocco.

In Morocco, the marine environment has always been a major occupation for socioeconomic activities (industry, tourism, urbanization, etc.). Thus, this work displays a case study of Taghazout coast in the central Atlantic part of the country, which becomes the center of several development projects, such as the touristic resort Taghazout Bay. In the aim to assess the health status of this coastal ecosystem, a multi-indicator approach based on the response of biomarkers in the wedge clam Donax trunculus was adopted during two years (2016/2017). The undertaken investigations on the response of biomarkers (AChE, GST, MDA, and CAT) in the sentinel species D. trunculus showed an activation of defense mechanisms in this bivalve, which would imply exposure to chemical stress in this ecosystem. The monitoring of seasonal bioaccumulation of cadmium (Cd), lead (Pb), and copper (Cu) by D. trunculus indicates that the bivalves collected have been exposed to these metal sources in the study area. In addition, the correlation study has reported a significant effect of environmental parameters on biomarker response. Overall, the multi-indicator approach has clearly revealed the health status of Taghazout coast registered in a coastal urbanization.

Microbiological assessment of marine and estuarine ecosystems using fecal indicator bacteria, Salmonella, Vibrio and antibiotic resistance pattern.

Marine and estuarine environments are often affected by microbiological contamination that adversely affects their use and severely impacts human health. To examine the influence of anthropogenic activities, this study used two different ecosystems in Agadir Bay, to compare fecal indicator bacteria (FIB) and bacterial pathogen profiles over two years. Vibrio target pathogens were detected at a high frequency (49.3%), while a low percentage (5.5%) was noted for Salmonella. Apart from those mentioned above, several other pathogenic bacteria were detected such as Cronobacter sakzakii, Pseudomonas fluorescens, and Aeromonas hydrophila. We also investigated the antimicrobial resistance of the pathogenic bacteria isolated. Salmonella strains were sensitive to all the antibiotics used, except ampicillin, amoxicillin + Ac clavulanic and chloramphenicol. And Vibrio strains were resistant to ampicillin, cephalothin, amikacin, and ciprofloxacin. This study highlights the limitations of FIB in assessing the microbiological quality and the importance of environmental surveys in understanding the distribution of pathogens.

Integration assay of bacteriological risks in marine environment using salmonella spp and multimarker response in the bivalve Donax trunculus: Novel biomonitoring approach.

Microbiological contamination is one of the riskiest forms of human contamination in seawater, which threaten the stability of ecosystems and human health. In this study, we study the accumulation of a pathogenic bacteria Salmonella spp; isolated from the marine environment, in the soft tissue of Donax trunculus (Mollusca, Bivalvia), a commonly used as a bioindicators species for aquatic ecosystems monitoring, under laboratory conditions during both exposure and recovery periods. These bacteria were added in seawater at three concentrations previously determined against sentinel specie at three exposure periods (24, 48 and 96 h). In a second series of experiments, exposed specimens were afterward transplanted to clean water to assess the recovery pattern. The mortality rate of bivalves was determined as biomarker of general stress. Our findings suggest that microbiological contamination by Salmonella spp was gradually incorporated into the body of D. trunculus causing a significant induction of enzymatic activity of acetylcholinesterase (AChE), Catalase (CAT), glutathione-S-transferase (GST) and malondialdehyde (MDA) levels, as a function of time and concentration. Exposure to a bacterial concentration of 5.104 bacteria/liter resulted in the mortality of more than 80% of the specimens. This study is to test the pathogenicity of Salmonella strains at concentrations close to those of the marine environment, and their effects on biomarkers, thus deducing the existence of an exponential relationship between bacterial concentrations and enzymatic response. The principal component analysis shows that the four biomarkers had similar variation with bacterial concentrations, while two groups were obtained to change following the exposure time (CAT-GST and AChE-MDA). This study provides new findings on the potential accumulation of pathogenic bacteria associated with neurotoxicity and oxidative stress in the wedge clam Donax trunculus.

Assessment of seasonal and spatial variation responses of integrated biomarkers in two marine sentinel bivalve species: Agadir Bay (Southern of Morocco).

The present study aims to assess the effects of contamination of the Agadir bay coasts using bivalves as a biomonitoring sentinel species. Seasonal variations of biochemical composition in terms of total protein content and oxidative stress biomarkers including glutathione-S-transferase, malondialdehyde, catalase and acetylcholinesterase were evaluated in the soft tissues of Scrobicularia plana and Donax trunculus specimens. The latter were collected from two sites in Agadir bay during two-year span (2018-2020). The Integrated Biomarker Response Index (IBR) was performed to classify the stress response in both species and to assess the level of exposure to xenobiotics. The data showed maximum annual values of acetylcholinesterase and malondialdehyde for Donax trunculus in Agadir beach (AG) with 6.25 nmol/mn/mg and 3 nmol/mg of protein, respectively. Those of catalase and glutathione-S-transferase for Scrobicularia plana in Oued Souss estuary (OS) were of 4.41 µmol/mn/mg and 14.43 nmol/mn/mg of protein, respectively. The studied species are considered good indicators in aquatic ecosystems.

Assessment of the marine ecotoxic state in the Moroccan coastal area Anza-Taghazout following the installation of two wastewater treatment plants: a multibiomarker study using Mytilus galloprovincialis.

The aim of the present study is the first to evaluate the ecotoxic state of the marine environment in Anza-Taghazout coasts (Morocco) after installation of two wastewater treatment plants using a natural population of marine bivalves Mytilus galloprovincialis. These coasts are exposed to many discharges generating, thus, different sources of pollutants. These pollutants can modulate the physiological responses of marine bivalves to environmental stress. In this context, a multibiomarker approach consisting of a battery of biomarker evaluation was used to assess the response of these species to stress. In the whole soft tissues of M. galloprovincialis, four biomarkers were evaluated as follows: acetylcholinesterase (AChE), glutathione S-transferase (GST), catalase (Cat), and malondialdehyde activity (MDA). In parallel, physico-chemical parameters were measured in the marine water of Anza-Taghazout within three selected sites: S1 considered as "hotspot" located at Anza city; S2 located near of Aourir city; and the third site, S3 "reference" located in Imouran beach. Our results showed that activities of both glutathione S-transferase and catalase were higher in M. galloprovincialis collected from site S1, but high values of malondialdehyde and acetylcholinesterase activities were observed successively at S3 and S2. Application of integrated biomarker response (IBR) index was suitable for classifying the stress response in the M. galloprovincialis but did not allow to evaluate the level of the xenobiotic exposure in the studied sites. The statistical results did not show any significant differences between the three studied sites, and therefore, S1 has recently become clean due to the installation of two wastewater treatment plants.

A Multibiomarker Approach to Assess the Health State of Coastal Ecosystem Receiving Desalination Plants in Agadir Bay, Morocco.

The present study aims to evaluate the initial health status of two stations receiving seawater desalination plants in Agadir Bay (Tifnit-Douira and Cap Ghir) and to assess their potential environmental impact on the marine ecosystem health. Six pairs of mussels (Mytilus galloprovincialis) were collected at six sampling sites on a monthly basis over two years. Each pair was homogenized to obtain the postmitochondrial fractions (S9). Toxicological effects were measured using a multibiomarker approach based on either acetylcholinesterase (AChE), glutathione S-transferase (GST), catalase (CAT), and malondialdehyde (MDA) rate. The results show a seasonal variation of the biomarkers: their activities increase in summer and decrease in spring and winter. High activities were recorded during summer in Cap Ghir (17.94 ± 0.88; 5.91 ± 052 nmol/min/mg of protein) for CAT and MDA, respectively. In Tifnit-Douira, low activities were recorded during winter for GST (3.74 ± 0.52 nmol/min/mg of protein) and during spring for the CAT (3.52 ± 0.45 nmol/min/mg of protein). The fluctuations in the activities of measured biomarkers could be attributed to different factors including the changes in environmental parameters, the influence of seasonal variation, and the contamination of the aquatic ecosystem. The data obtained in this study should be taken into account in the monitoring and management of the health of the ecosystems when the desalination plants are established.

Characteristics and dynamics of Salmonella contamination along the coast of Agadir, Morocco.

The occurrence of Salmonella enterica in the environment of tropical and desert regions has remained largely uninvestigated in many areas of the world, including Africa. In the present study, we investigated the presence of Salmonella spp. along 122 km of the coastline of Agadir (southern Morocco) in relation to environmental parameters. A total of 801 samples of seawater (243), marine sediment (279), and mussels (279) were collected from six sites between July 2004 and May 2008. The overall prevalence of Salmonella spp. was 7.1%, with the highest occurrence in mussels (10%), followed by sediment (6.8%) and seawater (4.1%). Only three serotypes were identified among the 57 Salmonella sp. strains isolated. S. enterica serotype Blockley represented 43.8% of all Salmonella strains and was identified in mussel and sediment samples. S. enterica serotype Kentucky (29.8%) was found almost exclusively in mussels, whereas S. enterica serotype Senftenberg (26.3%) was detected in sediment and seawater. Statistical analysis using generalized additive models identified seawater temperature, environmental temperature, rainfall, and solar radiation as significant factors associated with the presence of Salmonella. Rainfall was the only variable showing a linear positive effect on the presence of Salmonella in the sea, whereas the remaining variables showed more complex nonlinear effects. Twenty-eight (49.1%) Salmonella isolates displayed resistance to ampicillin (22 isolates), nalidixic acid (9 isolates), sulfonamide compounds (2 isolates), and tetracycline (1 isolate), with six of these isolates displaying multiple resistance to two of these antimicrobial agents. Pulsed-field gel electrophoresis analysis revealed homogenous restriction patterns within each serotype that were uncorrelated with the resistance pattern profiles.

Changes in the sediment trace metal contamination after the commissioning of a municipal wastewater treatment plant in the Souss estuary (South Morocco).

Monthly samples of sediment were collected from the Souss estuary, to determine the changes which have occurred in the concentrations of ten metals between 2001 when the low estuary was receiving the wastewaters from Agadir city and 2003 after stopping the sewage dumping. The annual contents of Cu, Fe, Zn (in 2001) and those of Cr, Cu, Fe, Mn, Ni, Pb, and Zn (in 2003) showed significant correlations with those of Al, indicating that fluctuations of their concentrations were only due to those of the aluminosilicate fraction of the clayey sediment. After normalization of these metallic concentrations in relation to those of Al, the contents of the different metals showed insignificant correlations between both years, except for Zn which significantly dropped in 2003 and Cu which increased in 2003. The observed metallic fluctuations are more influenced by the natural conditions of the estuary than the anthropogenic ones.