High bacterial loads occurs in beaches (e.g., Densu, Kpeshi and Ghana-Togo boarder) (Table 3) within coastal zones characterized by increased human activities such as densely populated coastal communities, industrialization, tourisms, beach Resorts, transboundary, swimming and fishing activities. While minimum bacteria load occur in Anyanui beach which is characterized by less populated fishing communities in the eastern coast of Ghana.
Principal components analysis indicated the beaches can be classified into four major clusters based on influential physicochemical parameters:(i) cluster 1; Anyanui beach located in the eastern coast is influence by freshwater flow from Volta River leading to low saline condition and controlled by chlorophyll-a concentration (ii) cluster 2; Ghana Côte d'Ivoire and Domonli beaches are situated in western coast and mostly influenced by high oxygenated sea waters (iii) cluster 3; Aboadzi, Kpeshi, Densu, Ghana-Togo border beaches are located in western-central-eastern coast and characterized by increased electrical conductivity, salinity, total dissolved solids and pH; and (iv) cluster 4; Amisa, Esiama and Muni beaches are situated in the central zone and characterized by high total suspended solids, phosphate and nitrates and redox potential (Fig. 2). The grouping of the beaches shows similar characteristics in their physicochemical composition of water quality.
The combination of physicochemical and bacteria data showed (Fig. 3) showed four major groups of beaches, mainly (i) Cluster 1; Kpeshi beach is major contaminated beach with high loads of total coliform and Escherichia coli. The Kpeshi beach is located at central of coast in the Greater-Accra region, Ghana. The beach is tourism center with two major hotels, La Beach Hotel and La Palm Hotel and the location is densely populated communities along the coast. The beach swimmers and discharge of waste by these hotels may have contributed to contamination of beach water with high bacterial loads; (ii) cluster 2; Ghana Côte d'Ivoire, Domonli and Aboadzi less contaminated beaches characterized by oxygenation. These beaches are located in western region where the population may be low and less frequent beach users and hotels (iii) cluster 3; Esiama, Muni, Anyanui and Ghana-Togo border beaches with moderated contaminated beaches characterized by chlorophyll-a concentration may have minimal human impact (iv) cluster 4; Amisa and Densu beaches with second major contaminated chacteracterised by Enterroccus sp. and nitrates. Densu beach is situated in area with high populated coastal vicinity and adjoining Densu beach Restort and Bojo beach coupled with connection to Densu estuary and subsequent Densu river. The Amisa Beach is connected with Amisa estuaries and connecting Amisa River. There is increasing human activities of fish farming, animal husbandry, water transportation in theses coastal systems which can cause increased in nutrients and bacteria load.
Nitrated and total dissolved solids significantly (p < 0.05) drive the spatial distribution of bacteria in beach water (Table 3). Enterococcus is mostly abundant in Esiama beach influenced by nitrated enrichment of the sea water. Whereas total coliforms and Escherichia coli abundant in Densu and Kpeshi beaches influenced by high levels of total dissolved solids of the seawater (Fig. 4). The correlation shows the linearity between salinity, conductivity and total dissolved solids. There is also significant linear association among the bacteria. The correlation between physiochemical and bacteria is confirmed by the principal component ordination
The lowest temperature (26.94 °C) was recorded at Aboadzi beach in western coast and the highest (30.82 °C) at Kpeshi beach in the central zone. Sea surface water temperature along the coast of Ghana ranged from 25.0 to 28.7 °C with mean ± SD 26.9 ± 1.28 °C, and Chorkor beach ranges from 24.5 to 28.7 °C with mean ± SD 27.2 ± 1.32 °C (Akita et al. 2014).Ghana is situated in the tropical equatorial climate belt with annual mean temperature between 25 °C and 36 °C (Allersma &Tilma 1993). In this region the sea surface water temperature only varies marginal throughout the year (Biney 1982, 1993). The coastal waters are thermally stratified with a well-mixed layer of warm (25oC – 36oC), low salinity water of 33.67–34.22 PSU in 30–40 m above a sharp thermocline (Mensah &Anang 1998). Salinity of 35.05–35.38 PSU below the thermocline at 60–80 depth. During upwelling, the thermocline weakens and rises to the surface resulting in vertically homogeneous salinity profile above the shelf (Mensah &Anang 1998). The lowest salinity (14.01 PSU scale) was recorded at Anyanui beach in the eastern coast due to freshwater intrusion from Volta River at Lower Volta Lake which also connects to Anyanui Lagoon, whereas the highest (34.70 PSU scale) in Densu beach in the central coast. Marine waters have a much higher conductivity than fresh to estuarine, ranged from 20.0 to 40.0 mS/cm). Salinity of sea water is normally 36 PSU scale. The salinity of coastal beach waters in Ghana ranged from 33.5 to 37.9 (PSU scale) with mean ± SDvalue 36.6 ± 1.53 (e.g., for La beach) and from 34.5 to 38.0 (PSU scale) with mean ± SDvalue 36.7 ± 1.21 (e.g., for La beach) (Akita et al. 2014). The lowest (8.30) pH was recorded in Esiama beach and the highest (9.05) at Domunli beach. The EU has set protection limits of pH ranged from 6 to 9 as harmless for fisheries and aquatic life (Chapman 1996). The pH values fall within the pH ranged between 6 and 9 for natural waters and pH 0f 8.30 for sea water (Stumn &Morgan 1981). The lowest (3.68 mg/l) dissolved oxygen concentration (DO) was recorded in Amisa beach and the highest (6.44 mg/L) at Densu beach. The nature of beach morphodynamics and hydrodynamic conditions may play role in circulation system of beach. Dissolved oxygen concentration is 7.0 mg/l for tropical surface waters (Biney 1993, Clark 2000) and unpolluted waterbodies of 8.0 to 10.0 mg/l at 25 °C (DFID 1999). Dissolved oxygen concentration is another important environmental variable used for water quality controls. Adequate oxygen maintains the biological life of the aquatic ecosystems. Dissolved oxygen concentration of 4–5 (mg/L) can sustain aquatic life. But below 5.0 (mg/L) may indicates high microbial activity and can adversely affects aquatic life (DFID 1999, Stumn &Morgan 1981). In extreme situations, decrease dissolve oxygen levels can lead to anoxic conditions, fish kills and odors resulting from anaerobic conditions (DFID 1999, Stumn &Morgan 1981). The lowest (61.80 mV) redox potential was recorded in Domunli beach and the highest (265.00 mV) at Kpeshi beach. A low redox potential corresponds to high pH as observed in Domunli beach. Higher redox potential means anoxic conditions as observed in Kpeshi. The redox potential for natural waters ranged from 500 to 600 mV (Stumn &Morgan 1981, Wetzel 2001). With depletion of oxygen, the redox potential decreased to 0 to 200 mV (Stumn &Morgan 1981, Wetzel 2001). The lowest total dissolved solids (11.71 mg/L) concentration was recorded at Anyanui beach and the highest (31.60 mg/L) at Densu beach. The lowest total suspended solids (4.00 g/L) concentration was recorded at the Ghana- Côte d'Ivoire, border beach and the highest (76.33 g/L) at Amisa beach which is connected to the Amisa Estuary, has tidal mixing and a large fishing industry. These activities may results in resuspension of minerals and salt particles through tidal influx and bottom trawling. High total dissolved solids in water originate from natural sources, urban and agricultural run-off, sewage discharges and industrial wastewater. The lowest phosphate (0.04 mg/l) concentration was recorded in Domunli beach and the highest (0.54 mg/L) at Amisa beach. The mean phosphate concentration of (0.18 ± 0.16 mg/L) is higher concentration in unpolluted, natural waters (ranged from 0.005 to 0.020 mg/L) (Biney 1993, Clark 2000) (Chapman 1996)., Phosphate concentration is as low as 0.001 mg/L in some pristine waters (Chapman 1996).,. Phosphate is the limiting nutrient for algal growth and therefore controls the primary productivity of a surface water body (Paerl et al. 2011). High concentrations of phosphate may indicate the presence of pollution and are largely responsible for eutrophic conditions (Omoike &Vanloon 1999, Saad &Younes 2006). The lowest nitrate (1.63 mg/L) concentration was recorded at Anyanui beach and the highest (3.57 mg/L) at Amisa beach. Nitrates in coastal beach waters of Ghana ranged from 0.5 to 0.25 to 1.8 mg/L in coastal waters of Ghana (Akita et al. 2014, Biney &Asmah 2010). Low nitrates occurs in unpolluted waters (Jaji et al. 2007). Nitrates is the most highly oxidised form of nitrogen compounds present in surface waters (Igobinosa &Okoh 2009). Nitrogen fixing bacteria and algae convert free nitrogen gas (N2) into nitrates (NO3-) (Igobinosa &Okoh 2009). Nitrogen waste products such as urea and uric acid are eventually converted to ammonia. The ammonia is then utilized by nitrate bacteria to form nitrites (NO2-), which are in turn are converted into nitrate. Phosphates and nitrates essential nutrients necessary for primary production and naturally replenished by river run-off (Correl 1998, Sharpley et al. 2013). Phosphates and nitrates are limiting nutrients for plant growth (Paerl &Huisman 2008). However, excess nutrients leads to phytoplankton blooms process often term as eutrophication (Kennish 2001, Nixon 1995, Smith &Schindler 2009). The major proportion of phosphate are transported to the aquatic environment from cultivated land usually in particulate form through erosion and leaching transports relatively little soluble P, as P is strongly adsorbed on clay particles (Carpenter et al. 1998, Elser et al. 2007, Sharpley et al. 2013).
The trophic state of beach water is classified as an ultra-oligotrophic to mesotrophic state based on chlorophyll-a concentration (0.43 to 6.13 µg/Ll Chlorophyll-a concentration in nears-shore coastal beach waters of Ghana ranged Chorkor beach (Akita et al. 2014). Chlorophyll-a concentration ranges from 0.10 to 3.80 mg/L (average 1.39 ± 0.84) in coastal waters of Caspian Sea. Very low and high levels of Chlorophyll-a concentration can be harmful to marine biota (Jamshidi &Abu Bakar 2011). Chlorophyll-a concentration act as an indicator of phytoplankton abundance and biomass in coastal ecosystems (Hinga et al. 1995, Monbet 1992). (Boyer et al. 2009, Bucci et al. 2012, Möller &Scharf 1986). Chlorophyll-a concentration provide an estimates of phytoplankton biomass and thus productivity of a water body (Boyer et al. 2009, Jamshidi et al. 2010, Tripathy et al. 2005, UNESCO 1994). Eutrophication is associated with increased phytoplankton blooms and increased primary production (Wellman et al. 2002). A positive relationship was found between the Chl-a concentration in the swash zone and biomass and numbers of macrofaunal species nutrition (Lastra et al. 2006).
Microbial water quality
The abundance (Table 1) of total coliforms Escherichia coli and Enteroccocus is low in Anyanui beach and the highest at Densu and Kpeshi beaches. The small communities have contributed low contamination at Anyanui beach. Whereas, Densu and Kpeshi beaches are characterized by densely populated human settlements, farming surrounding catchments estuaries, large industries, tourisms, beach resorts, hotels, large coastal fishing communities and popular sites for beach swimmers. The possible contamination sources include untreated disposal of human and animal waste and runoff from agricultural farmlands may affect the beach water quality. In the south-east Nigeria, maximum bacterial colony count (up to 60000 CFU/100 ml) and largest variability were found in mesotidal estuaries and adjoining near-shore waters (Anita &Showell 1997). In this study is limitation and variability was not evaluated due to 10-day short survey. However, the detection of Escherichia coli and Enteroccocus sp. in the coastal beach waters in Ghana provide evidence of faecal pollution, possibly from animal and human waste discharges. Total coliforms are found in animal intestines, in sediment on vegetation and in industrial waste. Escherichia coli often known as faecal coliform is found in natural inhabitant of the gastrointestinal tract of warmblooded animals and a direct evidence of faecal contamination. Faecal streptococci are found in faeces, however, some species live on plants and in sediment. Enterococcus sp. are a subset of faecal streptococci and commonly present in the faeces of warmblooded animals. Enterococcus are more persistent in water than coliforms. They provide a different assessment of the transport of faecal contamination in water than coliforms because of their different shape and survival rate (USEPA 2002). The presence of these faecal bacteria in marine waters can indicate the possible presence of disease causing bacteria, virus and protozoans (Crowther et al. 2001, Solic &Krstulovic 1992). These pathogens may pose health risks to fisher folks and beach swimmers and sea food consumption. Faecal bacteria indicate a pollution caused human and animal waste discharges (Savage 1905, Sayler et al. 1975, Schroeder &Wuertz 2003). Escherichia coli is mostly common in fresh and estuarine waters, whereas Enterococcus sp. is common in marine waters, good bioindicators of faecal contamination (Pachepsky &Shelton 2011). Agriculture runoff and domestic sewage waste water are often associated with high loads of bacteria (Schroeder &Wuertz 2003, Solo-Gabriele et al. 2000). Physicochemical variables such as salinity, temperature, nutrients and light, influence the survival and sometimes the proliferation of pathogens and bacteria (Cabral 2010, Pommepuy et al. 2005). The faecal bacteria are often used to detect water pollution (Odonkor &Ampofo 2013). Microbial contamination is a growing concern for environmental and human health (Odonkor &Ampofo 2013). Total coliform, Escherichia coli and Enterococcus sp. bacteria are used to indicate pathogens of faecal origin in surface and coastal water bodies (Table 2) (Guillaud et al. 1997, Medema et al. 2003). Escherichia coli and Enterococcus sp. can be found in intestinal bacteria of warm-blooded animals. Their presence in coastal waters serve as an indicator of potential sewage pollution. Total coliforms numbers include non-faecal bacteria, so additional testing is often done to confirm the presence and numbers of faecal bacteria. consequence of the vagaries of pathogen detection is the use of normal faecal bacteria as indicators of water pollution (Bettelheim 2003). Escherichia coli is the best bacterial indicator of faecal pollution (Stewart et al. 2008). But faecal enterococci are also used as complementary microbiological water quality indicator (Byamukama et al. 2000).
Table 1
Description of the coastal beaches of Ghana.
Beaches (Code) | Alternative names of beaches | Coastal zone | Human activities surrounding the beaches | Coordinates |
| | | | | Latitude | Longitude |
Gh-Côte: Ghana-Côte d’Ivoire border | New Town/ Ghana-Côte d’Ivoire border | Western | Transboundary activities in the western zone, water transportation, fishing, and domestic | | 5° 5.452'N | 3° 6.106'W |
Domunli | Jerusalem | Western | Domestic and fishing | | 5° 1.372'N | 2° 45.853'W |
Esiama | Esiama-Elimna | Western | Domestic and fishing | | 4° 55.895'N | 2° 20.957'W |
Aboadzi | Aboadzi Thermal Plant | Western | Industrialization, hydrothermal generation, domestic and fishing | | 4° 58.029'N | 1° 40.158'W |
Amisa | Amissano beach Amissano village | Central | Domestic and fishing | | 5° 12.123'N | 0° 59.849'W |
Muni | Apam | Central | Domestic and fishing | | 5° 19.611'N | 0° 38.842'W |
Densu | Bojo | Central | Industrialization, Urbanization, domestic, fishing, Agriculture, Aquaculture, mining | | 5° 30.403'N | 0° 19.718'W |
Kpeshi | La/Laboma | Central | Industrialization, Urbanization, Tourism, fishing, and domestic | | 5° 33.854'N | 0° 8.041'W |
Anyanui | Fuvenie | Eastern | Domestic and fishing, water transportation | | 5° 46.372'N | 0° 41.785'E |
Gh-Togo: Ghana-Togo border | Afloa/Ghana-Togo border | Eastern | Transboundary activities in the eastern zone; water transportation, fishing, and domestic | | 6° 6.493'N | 1° 11.319'E |
Escherichia coli and Enterococcus sp. in waters originate from domestic and animals waste discharges (Schroeder &Wuertz 2003). Waterborne diseases may impact public health (Fong &Lipp 2005, Mwabi et al. 2012). Bacteria in water is capable of transmitting disease such as cholera, typhoid fever, bacillary dysentery and diarrhea (Cabral 2010, Drasar 2003). The total coliform abundance in water (mean 4,061 ± 4,149.14) exceeded the mandatory levels for the water quality for swimming from most countries (Table 3). The mean total coliforms ranged between 1,136 and 1,880 CFU/100 ml, while the faecal coliforms ranged between 336 and 739 CFU/100 ml. When comparing with WHO standards (WHO 2008) the results suggest that the sanitary quality of the water is unacceptable. The faecal bacteria in coastal waters arise from discharges of untreated sewage or treated sewage effluent, either directly to the sea or via river systems, runoff from adjacent lands, especially from livestock farming (Kay et al. 1999a, Wyer et al. 1998) and faecal inputs from shore birds especially in the intertidal zone (Jones &Obiri-Danso 1999).
Microbiological water quality shows variation according to the magnitude of such inputs, the flux and dispersion of organisms as a result of near-shore hydrodynamics and the rate of die-off consequences of exposure to UV light (Davies-Colley et al. 1994, Solic &Krstulovic 1992). Microbial concentrations may differ along a particular stretch of the coast and can exhibit marked temporal fluctuations through the bathing season (Crowther et al. 2001, Kay et al. 1999b, Love et al. 2014, Obiri-Danso &Jones 1999). Untreated effluents discharges directly onto the coast can contribute to the microorganisms, in seawater and the microbes can be transported via the food chain into the seafood (Haas 2001, Metcalf 1982, Pommepuy et al. 2005). Bacteria pollution may impose potential health hazards and sea food contamination via transfer in the food chain. The presence of pathogenic microorganisms from sewage discharges leads to human and animal related diseases in seawater and seafood. For instance, human enteric viruses such as norovirus, astrovirus, rotavirus, hepatitis Avirus and pathogenic bacteria including Salmonella, Listeria monocytogenes, Shiga-toxin-producing Escherichia coli, Vibrio cholerae, Vibrio parahaemolyticus causing diseases have been associated with faecal contamination in coastal waters (Bosch et al. 2001, Grimes 1991, Kong et al. 2002, Metcalf 1978, Rothenheber 2017). Microorganisms can cause infections such as gastrointestinal and respiratory illnesses, skin diseases and eye infections (Griffin et al. 2003).