Assessing the phytoplankton and water quality of Kingston Harbour and Hellshire coast, Jamaica, after the implementation of a waste water treatment facility
Evaluación de la calidad de las aguas de la Bahía de kingston y la costa Hellshire, Jamaica, después de la implementación de una planta de tratamiento de aguas residuales
Helen A. Liu1*, Sheree A. Broomfield1, ]]>
1, Leon O. Grant1, Patrice A. Francis1, Dale F. Webber1 & Mona K. Webber1
Abstract
Deteriorating water quality of ]]>
BOD5, faecal coliform and nitrate concentrations indicated that the water quality had improved minimally in Kinsgton and Hellshire,and deteriorated significantly in Hunts. Phytoplankton biomass decreased in Kingston (from 3.84 mg m-3 in 1998 to 2.81 mg m-3 in 2011) and increased significantly in Hunts (from 14.69 mg m-3 in 1998 to 24.17 mg m-3 in 2011). Biomass along Hellshire was similar (2.15 mg m-3 in 1998; 2.45 mg m-3 in 2011). In 1998 the nanoplankton biomass (2.7 to 20μm) dominated throughout the Harbour. In 2011 Hunts Bay was dominated by net-plankton (>20μm), indicative of eutrophic waters.
El deterioro de la calidad del agua del puerto de Kingston es debido principalmente a la descarga de aguas residuales y su efecto en los alrededores de la Costa de Hellshire, esto ha sido un ]]>
BOD5, coliformes fecales y concentraciones de nitratos indicaron que había mejorado la calidad del agua del puerto y la costa mínimamente mientras que la calidad del agua en la bahía Hunts se había deteriorado significativamente. La biomasa del fitoplancton disminuyó en el ]]>
m-3 en 1998 a 2.81mg m-3 en el 2011), y aumentó significativamente en bahía Hunts (de 14.69mg m-3 en 1998 a 24.17mg m-3 en el 2011). La biomasa en la costa permaneció similar (de 2.15mg m-3 en 1998 a 2.45mg m-3 en 2011). En 1998 la biomasa de nanoplancton (2.7 a 20μm) dominó a lo largo del puerto. En el 2011 la bahía Hunts era dominada por neto-plancton (>20μm), indicativo de aguas eutróficas.
Palabras clave: Soapberry, aguas residuales, Puerto de Kingston, eutrofización, Bahía Hunts, Hellshire
Kingston Harbour on the south east ]]>
Spatially assess and ]]>
Determine if there was significant improvement or deterioration in water quality when compared to the earlier baseline studies (i.e. prior to the Soapberry waste treatment implementation).
Materials and Methods
Sample programme: A total of four sampling sessions were conducted during the period of May 21st to June 19th,2011, between the hours of 0700hours and 1200hours. Eleven stations (Fig. 1) were strategically selected along the North East Hellshire coastline (Stations 1-3), throughout Kingston Harbour (Stations 4–7) and in Hunts Bay (Stations 8–11), and based on previous studies by Webber and Roff (1996), Dunbar (1997), Ranston (1998) and Webber & Webber (1998). At each station physicochemical parameters were recorded using a Hydrolab Surveyor with a Datasonde 5 multi-parameter probe and whole water samples were collected at (i) the surface and (ii) 2m above the substrate (±0.10oC temperature; ±0.2ppt Salinity; ±0.01mg l-1 LDO; ±1.0NTU Turbidity; and ±0.2units pH).
Whole water samples: Samples were collected from the surface (fresh water) layer as well as the underlying deeper (more saline layer) using a 6L Niskin bottle. At Hunts Bay, surface samples were collected (i) just below the surface of the water and (ii) deeper samples at 2m above the substrate using a horizontal position Niskin bottle (Ranston, 1998). An aliquot of each water sample was then transferred to 3L plastic bottles and kept in the dark until filtration was possible, generally within four hours of collection. The samples for Biochemical Oxygen Demand (BOD) analysis were collected in 300mL BOD bottles then stored on ice for three (3) hours, prior to analysis. A YSI Model 57 Oxygen meter (±0.1mg l-1 on 0-10 scale) was used to determine the initial dissolved oxygen of each sample. Samples were then incubated for five (5) days at 20oC in total darkness with subsequent re-testing for dissolved oxygen (Eaton, Clesceri & Greenberg, 1995; Webber & Wilson-Kelly, 2003). The BOD5 for each sample was derived using the formula: BOD5 = [(Initial DO-Final DO) × (1 000mL)]/300mL).
The 3L samples were filtered through a size fractioning tower with three filters of known pore sizes (Nitex screening: 20μm, Whatman glassfibre filters (GFD): 2.7μm and Whatman glassfibre filters (GFF): 0.7μm). Samples were gently homogenised prior to filtration. Two pseudo-replicates for each station at each depth were then poured through the fractionating tower. Size fractioning filtration was done within four hours of collection time (Parsons, Maita & Lalli, 1984). Each filter was rolled and then placed in labelled vials and stored in a freezer for later Chlorophyll α analysis. Chlorophyll α was extracted using 90% acetone (Parsons et al.,1984) under dark conditions for 24 hours in a refrigerator (Ranston, 1998). Each extracted sample was read on a Turner Flourometer TD-700. Values were recorded within 12 seconds of cuvettes being placed into the flourometer. Samples that contained high Chlorophyll that could not be read by the flourometer were diluted as outlined in Parsons et al. (1984). Chlorophyll α was calculated using the formula:
mg Chlorophyll α m-3 = R x (ν/V) x Dilution Factor
(Parsons et al., 1984)
Where: R = Flourometer reading; ν = acetone extraction volume (mL); V = volume of seawater filtered (l)
Nutrient Analysis: Approximately 250mL of the filtrate from the size fractioning tower for each station was frozen for nutrient analysis. Nutrient samples were analysed on a Lachat QuickChem 8 000 Flow Injection Analyser (±0.001mg l-1), using sulfanilamide colour reagent, ammonium chloride buffer, and a cadmium reduction column. Samples were run with the cadmium column online for total nitrate+nitrite analysis, and offline for phosphate and nitrate analysis.
Bacteriological analysis: Coliform bacterial density was determined as Most Probable Number (MPN) counts using the multiple tubes fermentation technique. A series of dilutions of the samples were prepared; these dilutions were 1.0mL, 0.1mL and 0.01mL. Five aliquots of each were inoculated into the growth medium and were incubated. A positive score was recorded whenever bubbles were formed as a result of fermentation. Lauryl Tryptose broth formed the presumptive phase and Escherichia coli broth medium with Durham inverted tube formed the confirmatory phase (Eaton et al., 1995).
Results
The one month survey of the water quality of the Kingston Harbour provided important insight into the changes in that body of water. These changes were as a result of the introduction of a diverted sewage discharge over a short time period. The evidence of the spatial changes in key water quality parameters are divided here into physicochemical and biological indices.
Physiochemical indices: Temperature, salinity, dissolved oxygen; turbidity and pH were all within the expected ranges for coastal nearshore systems and demonstrated the spatial pattern consistent with the findings of Webber & Webber (1998). Lowest salinity and temperature accompanied by highest dissolved oxygen and pH were evident in Hunts Bay, while highest salinity and temperature and lowest pH were observed along the Hellshire Coast. There were also no significant differences in physicochemical indices in the 2011 study when compared to data collected in the surveys from the 1990’s.
Nitrate-N concentrations were spatially variable with the expected increase from the previously classified mesotrophic Hellshire Coast, into the eutrophic Hunts Bay. The concentrations of nitrates were lowest along the Hellshire coast (0.63 to 0.78mg l-1 at stations 2 and 3), marginally higher in the Kingston Harbour (0.63 to 0.94mg l-1 at stations 6 and 7) and highest in Hunts Bay (1.45mg l-1 at station 9). While nitrate concentrations were much lower in 2011 than in the 1990’s (Fig. 2) values in both studies were higher than the NEPA (2009) ambient marine water quality nitrate standard of 0.007-0.014 mg l-1.
Biological indices: Mean phytoplankton biomass (as Chlorophyll α) in the 2011 study increased from the Hellshire Coast (1.8 to 2.19mg m-3 at Stations 2 and 3) into the Kingston Harbour (1.7 to 3.8mg m-3 at stations 6 and 7) and reached a maximum in Hunts Bay (12.6 to 33.1mg m-3 at stations 8–11). While this spatial pattern was similar to the 1998 studies, t-tests revealed significant difference (p= 0.02) between the two studies. The highest biomass in 1990’s of 13.5 mg m-3 was observed in Hunts Bay with lowest values at Hellshire Bay 1.38mg m-3. Phytoplankton biomass in the Kingston Harbour was however unchanged between 1990’s and 1998. The single exception was at station 6 where biomass values decreased from 4.17 to 1.70 mg m-3 between 1998 and 2011. Both surface and deep water phytoplankton biomass in 2011 were greater than in the 1990’s except at stations 9 and 11 (Hunts Bay) where sub-surface biomass in 1990’s were greater than 2011 (Fig. 3a, b, c & d).
The nanoplankton biomass size fraction dominated surface waters at all stations in both the 2011 and 1990’s studies, although the net plankton biomass size fraction accounted for a larger proportion of total phytoplankton biomass in the 2011 samples. This was especially so in Hunts Bay (stations 8-11) which clearly reflected that deep waters were dominated by the net plankton biomass size fraction (Fig. 3c & 3d).
Faecal coliform counts increased from station 1 along Hellshire coast to station 9 in Hunts Bay (Fig. 4). Coliform concentration ranged from <20 to 1 200MPN/100mL with highest concentration at station 9, while the lowest concentrations were found at stations 1 to 3 (Hellshire Coast). Apart from station 9 in Hunts Bay all other values were below the World Health Organization (WHO) 1988 standard of 1 000MPN/100 mL (Owili, 2003) but higher than the National Environment and Planning Agency [NEPA], 2009) standard of <2-13MPN/100mL for ambient marine waters. Faecal coliform counts along the North East Hellshire coast and in the Kingston Harbour were generally lower in the 2011 (20 to 300MPN/100 mL) than the 1990’s (>500MPN/100 mL) while counts in Hunts Bay were higher in 2011 (>2 400MPN/100 mL) than in the 1990’s (1 200MPN/100 mL). ]]>
The BOD5 values recorded in both studies ranged from 1 to 52mg l-1. The lowest BOD5 value was recorded along the Hellshire Coast at station 3 (2.8mg l-1) in 2011 and station 1 (1mg l-1) in 1990’s. While samples from the Kingston Harbour were observed to have much reduced BOD5 in 2011(4.6 to 4.9mg l-1) over the 1998 data (10-35mg l-1), water samples from Hunts Bay were observed to consistently have the highest BOD5 in both studies 50 to 52mg l-1 (Fig. 5).
Discussion
Physico-chemical ]]>
A specified ]]>
l-1 can still be indicative of unpolluted waters. Therefore Kingston Harbour nitrate values are not a good index of water quality. However, lower nitrate values in the Kingston Harbour and Hellshire coast suggest a reduction in nutrient input or uptake by the biota resulting in improved water quality.
Using the Faecal coliform bacteria ]]>
Biochemical Oxygen Demand values obtained for each station surpassed the range (1.16mg l-1) set out by ]]>
BOD5 and thus the poorest water quality and the Harbour and Hellshire Coast both having similar but lower BOD5 values (2.8 to 4.8mg l-1). This was also expected since Hunts Bay is almost totally enclosed and receives inflows from (i) Sandy Gully which is the largest storm water drainage gully in the City of Kingston, (ii) the Rio Cobre which drains extensive farming areas of Jamaica as well as (iii) the newly commissioned Soapberry Treatment Facility. The significantly lower BOD5 values observed in 2011 compared with the 1990’s values indicate that ]]>
Nutrients, water clarity, biochemical oxygen demand, chemical contaminants and bacteria are the indices frequently employed in determining water quality. Although the planktonic community is tedious to analyse, it is perhaps the most ]]>
Total phytoplankton biomass values as Chlorophyll α, were generally higher for all stations located in ]]>
m-3 while values ranged between 12 and 20mg m-3 in waters that were influenced by untreated sewage effluent. Hunts Bay values are extremely elevated (33.1mg m-3) compared with Thompson & Ho (1981) values. This suggests that Hunts Bay is ]]>
m-3. The pattern was repeated for subsurface total biomass with Hunts Bay demonstrating reduced water quality. However Kingston Harbour and Hellshire Coast had lower total biomass values indicating improved water quality.
]]>
Simmonds (1997) and Ranston (1998) found that the waters throughout Kingston Harbour and Hunts Bay were dominated by the nanoplankton Chlorophyll a size fraction which accounted for more than 50% of the standing crop. Ranston and Webber (2003) determined that there was a sporadic enrichment of relatively higher concentrations of nutrients, which could occasionally support greater proportions of net plankton biomass throughout Hunts Bay. The 2011 dominance of the net plankton size fraction biomass in both the surface and the deep values in Hunts Bay suggest that nutrient inputs ]]>
Another possible explanation for ]]>
The comparison between this study and the one conducted by Webber and Webber (1998) provides evidence that the water quality in the Kingston Harbour has indeed improved over the 15 year period due to the 73% reduction seen in nitrates, 82% reduction in Biochemical Oxygen Demand and 50% reduction in ]]>
Acknowledgments
We thank the staff ]]>
References
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1. Centre for Marine Sciences, Department of Life Sciences, The University of the West Indies, Mona, Kingston 7, Jamaica W.I.; dale.webber@uwimona.edu.jm
Received 29-IX-2013 Corrected 12-III-2014 Accepted 24-III-2014
