Phytoplankton Community Indicators of Short- and Long-term Ecological Change in the Anthropogenically and Climatically Impacted Neuse River Estuary, North Carolina, USA

Abstract

Estuarine and coastal systems represent a challenge when it comes to determining the causes of ecological change because human and natural perturbations often interact. Phytoplankton biomass (chlorophyll a) and group-specific photopigment indicators were examined from 1994 to 2007 to assess community responses to nutrient and climatic perturbations in the Neuse River Estuary, NC. This system experienced nutrient enrichment and hydrologic variability, including droughts, and an increase in hurricanes. Freshwater input strongly interacted with supplies of the limiting nutrient nitrogen (N) and temperature to determine the location, magnitude, and composition of phytoplankton biomass. Multi-annual, seasonal, and episodic hydrologic perturbations, including changes in the frequency and intensity of tropical storms, hurricanes and droughts, caused significant shifts in phytoplankton community structure. Climatic oscillations can at times overwhelm anthropogenic nutrient inputs in terms of controlling algal bloom thresholds, duration, and spatial extent. Eutrophication models should incorporate climatically driven changes to better predict phytoplankton community responses to nutrient inputs and other anthropogenic perturbations.

Spatial and seasonal variation of microphytoplankton community and the correlation with environmental parameters in a hypereutrophic tropical estuary - Maranhão - Brazil

“…However, it does not happen spatially, once the algal bloom was potentiated by high concentrations of nutrients. The entry of nutrients can occur naturally through runoff, or through the discharge of domestic sewage (THOMAS et al, 2005;PAERL et al, 2010;SOUZA et al, 2014), and when dominants (ammonium and phosphorus) the N:P ratio is less than the Redfield ratio 16:1 (COELHO et al, 2015;SILVA et al, 2015).…”

Molecular insights into a dinoflagellate bloom

“…Phosphate concentrations were relatively consistent throughout the estuary, whereas nitrate concentrations were more variable, but, in general, were high at the head of the estuary and decreased down-estuary from an annual mean of 34 μmol l − 1 at station 20 to commonly being below the detection limit by station 120. High variability in nitrate along the transect, particularly at the midestuary stations, is primarily due to fluctuations in river flow (Paerl et al, 2010). Chlorophyll a concentrations were consistently lower at station 20 and peaked at mid-estuary stations with an annual average of 25 μg l − 1 before steadily declining downestuary ( Figure 1c).…”

Temporal variability of chlorophyll-a in the São Vicente estuary

“…WHITFIELD; BRUTON, 1989). In the São Vicente estuary, episodic increments in water discharge due to HB scape pipes clearly affected the frequency of natural summer blooms, as has been observed in other estuaries (NIXON, 2003;LEPAGE;INGRAM, 1986). These events may certainly modify the adjacent continental shelf waters (see CARVALHO et al, submitted).…”

“…Changes in continental runoff also affect estuarine turbidity depending on its particle load and result from the precipitation rates over the estuarine system. In large estuarine systems, freshwater inflow can favor phytoplankton growth through the resulting input of nutrients (PAERL et al, 2009) or by promoting a vertical salinity stratification that retains phytoplankton in a nutrient-rich and well illuminated zone (CLOERN, 1991). Nonetheless, intense freshwater runoff episodes in small estuarine systems may flush out the local phytoplankton community (DE MADARIAGA et.…”

“…Agriculture residuals (NIXON, 1995) and sewage input in coastal environments (CARPENTER et al, 1998) are the main anthropogenic cause of water enrichment and the increase of phytoplankton biomass. The control of the freshwater flow (PETERSEN et al, 2008;DYNESIUS;NILSSON, 1994) and river damming (NIXON, 2003) often disrupt the spatial distribution, temporal patterns and community structure of phytoplankton by leading to changes in river-coast chemistry (HUMBORG et al, 2000). Thus, estuaries where human occupation is intense will benefit from monitoring programs that include the observation of phytoplankton dynamics.…”