Brackish waters are commonly characterised by high productivity due to frequent if not continuous inputs of nutrients from both freshwater (notably nitrogen) and marine (notably phosphorous) sources (Nixon 1995). Significant settlement of particulate matter, itself often rich in nutrients (including organic carbon), occurs in estuaries and can result in high levels of production of benthic (seabed) fauna and flora, and form a source of nutrients to the water column. These nutrients promote the growth of phytoplankton and algal blooms may occur. Such high productivity, combined with alternating salinity and temperature conditions, can result in fluctuating oxygen levels. These disturbances, and often extreme environmental conditions, result in estuaries and brackish environmental waters being characterised by a low biodiversity, but often high production of plants and animals.
Alga blooms can produce toxins which stress or kill aquatic life, contaminate shellfish and limit the value of the water body for public and recreational use. Toxic blooms in freshwater are correlated with nutrient enrichment (Petersen et al. 1999) and such pollution may also have a role in marine and estuarine toxic alga blooms.

Disturbed ecosystem conditions and low biodiversity in brackish waters are natural and not a management problem. However, if eutrophic conditions develop then benthic and/or planktonic alga blooms, and loss of species of economic importance (e.g. fisheries) can be a problem (e.g. Caddy 1993). Alga blooms can be unsightly, and can die on-mass and cause severe local anoxic conditions with hydrogen sulphide emissions. Apart from the upset such smells and pollution of seashores may cause to the public, they also kill off other fauna and flora. In 1988, the hydrogen sulphide released from the decay of over 1 million tons of the benthic alga Ulva in the Venice lagoon was so severe that evacuation of the city was considered (Runca et al. 1996).

The fauna living on the riverbed is routinely used as an indicator of river quality. Similarly marine seabed (i.e. benthic) fauna can indicate organic enrichment. However, within an estuary the benthic fauna can be exposed to salinity and temperature changes, and natural enrichment from settlement of particulate organic matter (i.e. mud). It can thus be difficult to discriminate impacts on estuarine benthos due to human activities. However, indices of estuarine quality have been developed that utilise information on the benthos (e.g. Jeffrey et al. 1985a, Jeffrey et al. 1985b).

Benthic fauna can be important in grazing algae, and aerating and stabilising sediments. Stabilisation of sediments by benthic plants (e.g. sea grass) and animals (e.g. tubeworms, hydroids) can reduce re-suspension of organic carbon into the water column. Furthermore, degradation of organic matter is faster under aerobic conditions through both microbial and
faunal activity. The extinction of fauna due to anoxia following alga blooms may thus make the recurrence of such blooms more likely in the future. For these reasons, regular surveys of species? distributions form a useful indicator of ecosystem health, complement monitoring of anthropogenic waste inputs, and provide a baseline for comparison against future surveys.

The best indicators of estuary trophic status may be the frequency (in time) and spatial extent of alga blooms, hypoxia in the water column, and the occurrence of impoverished benthos due to anoxia or other pollution. Service et al. (1996) considered eutrophic estuaries to exhibit a selection of the following: elevated nitrate concentrations in water; exceptional algal concentrations; long-lasting algal blooms; oxygen deficiency; changes in benthic fauna; changes in macrophyte growth; occurrence of shellfish poisoning; formation of algal scums.

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Costello, J.   "MEASUREMENT AND MODELLING OF NUTRIENT DYNAMICS OF TWO ESTUARIES IN IRELAND, WEXFORD AND CORK HARBOURS". Associated datasets and digitial information objects connected to this resource are available at: Secure Archive For Environmental Research Data (SAFER) managed by Environmental Protection Agency Ireland https://eparesearch.epa.ie/safer/resource?id=c71de499-204a-102f-a0a4-f81fb11d7d1c (Last Accessed: 2025-03-22)

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SAFER-Data Display URL	https://eparesearch.epa.ie/safer/iso19115/display?isoID=220
Resource Keywords	Nutrient Dynamics, Urbanisation, Drainage, Estuary
EPA/ERTDI/STRIVE Project Code	-
EPA/ERTDI/STRIVE Project Theme	Water Quality
Resource Availability:	Public-Open
Limitations on the use of this Resource	Any attached datasets, data files, or information objects can be downloaded for further use in scientific applications under the condition that the source is properly quoted and cited in published papers, journals, websites, presentations, books, etc. Before downloading, users must agree to the "Conditions of Download and Access" from SAFER-Data. These appear before download. Users of the data should also communicate with the original authors/owners of this resource if they are uncertain about any aspect of the data or information provided before further usage.
Number of Attached Files (Publicly and Openly Available for Download):	1
Project Start Date	Monday 19th January 1998 (19-01-1998)
Earliest Recorded Date within any attached datasets or digital objects	Monday 19th January 1998 (19-01-1998)
Most Recent Recorded Date within any attached datasets or digital objects	Monday 18th December 2000 (18-12-2000)
Published on SAFER	Thursday 25th August 2011 (25-08-2011)
Date of Last Edit	Thursday 25th August 2011 at 10:29:56 (25-08-2011)
Datasets or Files Updated On	Thursday 25th August 2011 at 10:29:56 (25-08-2011)

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Description of Geographical Characteristics of This Project or Dataset
The main rivers entering Wexford and Cork Harbours are the Slaney and Lee. In both cases, the entire estuary from the freshwater river to marine entrance to the sea is termed the ?Harbour?. Their freshwater catchment areas are similar, but freshwater runoff is greater in Cork due to a generally higher rainfall (Table 3). Wexford is smaller and shallower, and although it has a larger tidal range a greater proportion of its volume (39 %) is potentially exchanged on each tide than for Cork (10 %) (Table 3). They differ markedly in shape, the Slaney discharging into a very wide shallow bay (Figure 3), but the Lee into a narrower complex inlet (Figure 4). Both receive untreated sewage discharges, and Cork Harbour has a greater concentration of industrial discharges and a larger human population (Table 3). In Wexford Harbour, considerable areas of saltmarsh have been dyked off and drained for use as agricultural land. Large beds of mussels (Mytilus edulis) are managed as a fishery in Wexford Harbour, and Cork Harbour has a large native oyster (Ostrea edulis) farm. Phytoplankton blooms have caused concern in both estuaries. These were toxic dinoflagellates in Cork and nuisance mats of Phaeocystis washed ashore in Wexford Harbour.

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In this section some supplementary information about this resource is outlined. Lineage information helps us to understand why this project was carried out, what policy or research requirements did it fulfil, etc. Lineage is important in understanding the rationale behind the carrying out of a project or the collection of a specific dataset etc. Links to web sites, applications, papers, etc are outlined to provide you with additional information or supplementary reading about the project or dataset

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The following is a list of projects, datasets, and resources on SAFER-Data from which users downloaded attachments from soon after downloading attachments from this resource MEASUREMENT AND MODELLING OF NUTRIENT DYNAMICS OF TWO ESTUARIES IN IRELAND, WEXFORD AND CORK HARBOURS. You can view the full description for projects, datasets, and resources by using the links supplied.

• Identification of refereNce-Status for Irish lake typoloGies using palaeolimnological metHods and Techniques (IN-SIGHT) View Full Metadata Description
• Clarianna Rver Catchment - Raw Data Collection View Full Metadata Description
• Phosphorus, Nitrogen and Suspended Sediment loss from Soil to Water from Agricultural Grassland View Full Metadata Description
• Water Quality characteristics of road runoff View Full Metadata Description
• Quantification of Erosion and Phosphorus Release from a Peat Soil Forest Catchment View Full Metadata Description

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