Environmental Engineering Reference
In-Depth Information
Ta b l e 3 . 1 5 Algal Bioindicators of Estuarine Pollution: Episodic and Seasonal Events in Southern US Estuaries.
Estuarine System
Source of Eutrophication
Algal Analysis: Results a
Neuse River
estuary,
North Carolina
High rainfall - hurricanes in 1999
Pollution source - agricultural
urban and industrial activities
River discharge into estuary - elevated biomass (chl- a ),
increased chlorophytes/diatom populations, seasonal
changes - reduced dinoflagellate bloom.
Galveston Bay,
Texas
High rainfall - tropical storm in 2000 Freshwater flushed into bay, resulting in reduced salinity,
increased DIN plus blooms of cryptophytes and
dinoflagellates. Adverse effects on oyster beds
St. Johns River
Estuarine
System, Florida
High summer rainfall. Accelerating
point and diffuse nutrient loading
from watershed
Seasonal nutrient enrichment from watershed. Leading to
blue-green algal blooms, fish kills,
submerged-vegetation loss, wildlife mortalities
Source : Paerl et al ., 2005. Reproduced with permission from Taylor and Francis.
a HPLC diagnostic photopigment determinations coupled to ChemTax ® analysis
pigment analysis only resolves phytoplankton com-
munities to the major group (phylum) level, the
results obtained give clear information on the algal
response to environmental change and enable these
organisms to be used as bioindicators.
The use of HPLC/ChemTax analysis is reported by
Paerl et al . (2005) for various southern US estuarine
systems (Table 3.15), including the Neuse River Estu-
ary (North Carolina), Galveston Bay (Texas) and St.
Johns River (Florida). In all of these cases, eutroph-
ication occurs due to flushing of high volumes of
nutrient-rich freshwater into the lower reaches of the
estuary and into the surrounding ocean. The source
of nutrients primarily results from agricultural, urban
and industrial activities in the watershed, and flush-
ing occurs due to high rainfall - which may be sea-
sonal (summer wet season) or episodic (hurricane and
storm effects).
flow (reduced residence time), where algae with rapid
growth and short generation time (r-selected organ-
isms) are able to dominate more slow growing algae
(K-selected organisms).
Galveston Bay Eutrophication resulting from
tropical storms in 2000 led to increased algal growth
in the bay, with HPLC analysis indicating growths
particularly of cryptophytes and peridinin-containing
dinoflagellates. The location of the algal blooms
overlapped with commercial oyster reefs, leading to
ingestion of phycoerythrin-containing cryptophytes
and a commercially disastrous red/pink coloration of
the oysters.
St. Johns River system This is a 300 mile-long
estuarinesystemcomposedoflakes,tributaries,river-
sine segments and springsheds. Eutrophication was
indicated by extensive blooms of blue-green algae,
which dominated the relatively static parts of the sys-
tem such as freshwater lakes and various oligohaline
(low salinity) sites. These blooms have been associ-
ated with fish kills, loss of macrophytes and wildlife
mortalities.
NeuseRiverEstuary Thisaquaticsystemissub-
ject to alternations of high river discharge (seasonal
and hurricane rainfall) with periods of low discharge
(no rainfall). Algal bioindicators indicate phases of
eutrophication resulting from high freshwater flow
in relation to biomass increase (up to 19 μg chl-
a l −1 ) and a switch in phytoplankton populations -
promoting growth of chlorophytes and diatoms, but
reducing levels of blue-green algae and dinoflagel-
lates. This apparent reversal of the normal effects of
eutrophication is due to the conditions of high water
Eutrophication: molecular detection
of indicator algae
Freshwater plume Outflow of freshwater from
rivers creates a fluctuating zone of fresh (brackish)
 
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