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1.
Nathan S. Hall R. Wayne Litaker Elizabeth Fensin Jason E. Adolf Holly A. Bowers Allen R. Place Hans W. Paerl 《Estuaries and Coasts》2008,31(2):402-418
A dense bloom of the ichthyotoxic dinoflagellate Karlodinium veneficum was discovered in the Neuse River Estuary, North Carolina, on 19 October 2006 and was associated with four subsequent fish
kills. Microscopic, photopigment, DNA, and toxicological techniques confirmed bloom identity and toxicity. High-resolution
spatio-temporal data from ship-board and fixed automated sampling stations provided a unique opportunity to investigate the
environmental conditions that initiated, maintained, and terminated the K. veneficum bloom. Bloom initiation and growth were favored by high nutrient availability and reduced dispersal during the period of
declining riverine discharge after Tropical Storm Ernesto. K. veneficum out-competed other co-occurring dinoflagellates, perhaps because of the production of karlotoxins that are known to act as
grazing deterrents and to facilitate mixotrophic feeding. Once the bloom was established, small-scale hydrodynamic processes,
coupled with vertical migration, concentrated cells along a frontal convergence to high densities (>200,000 cells per milliliter).
By 26 October 2006, wind mixing and possible nutrient stress disrupted the bloom. Release of cell-bound toxins during the
bloom collapse likely accounted for the associated fish kill events where fish were reported as exhibiting typical symptoms
of karlotoxin poisoning. The dynamics of this bloom underscore the tight control of harmful algal blooms by meteorological
forcing, hydrology, and sediment nutrient input in this shallow lagoonal estuary. 相似文献
2.
Denitrification rates measured along a salinity gradient in the eutrophic Neuse River estuary, North Carolina, USA 总被引：2，自引：0，他引：2
John M. Fear Suzanne P. Thompson Thomas E. Gallo Hans W. Paerl 《Estuaries and Coasts》2005,28(4):608-619
Denitrification rates along a salinity gradient in the eutrophic Neuse River Estuary, North Carolina, were quantified using
membrane inlet mass spectrometry (MIMS) within short-term batch incubations. Denitrification rates within the system were
highly variable, ranging from 0 to 275 μmol N m−2 h−1. Intrasite variability increased with salinity, but no significant differences were observed across the salinity gradient.
Denitrification rates were positively correlated with sediment oxygen demand at the upstream sampling site where sediment
organic carbon levels were lowest. This relationship was not observed in the more saline sampling sites. Denitrification rates
were highest during winter. On an annual basis, denitrification accounted for 26% of the dissolved inorganic nitrogen and
12% of the total nitrogen supplied to the system. 相似文献
3.
L. W. HardingJr. C. L. Gallegos E. S. Perry W. D. Miller J. E. Adolf M. E. Mallonee H. W. Paerl 《Estuaries and Coasts》2016,39(3):664-681
Climate effects on hydrology impart high variability to water-quality properties, including nutrient loadings, concentrations, and phytoplankton biomass as chlorophyll-a (chl-a), in estuarine and coastal ecosystems. Resolving long-term trends of these properties requires that we distinguish climate effects from secular changes reflecting anthropogenic eutrophication. Here, we test the hypothesis that strong climatic contrasts leading to irregular dry and wet periods contribute significantly to interannual variability of mean annual values of water-quality properties using in situ data for Chesapeake Bay. Climate effects are quantified using annual freshwater discharge from the Susquehanna River together with a synoptic climatology for the Chesapeake Bay region based on predominant sea-level pressure patterns. Time series of water-quality properties are analyzed using historical (1945–1983) and recent (1984–2012) data for the bay adjusted for climate effects on hydrology. Contemporary monitoring by the Chesapeake Bay Program (CBP) provides data for a period since mid-1984 that is significantly impacted by anthropogenic eutrophication, while historical data back to 1945 serve as historical context for a period prior to severe impairments. The generalized additive model (GAM) and the generalized additive mixed model (GAMM) are developed for nutrient loadings and concentrations (total nitrogen—TN, nitrate?+?nitrate—NO2?+?NO3) at the Susquehanna River and water-quality properties in the bay proper, including dissolved nutrients (NO2?+?NO3, orthophosphate—PO4), chl-a, diffuse light attenuation coefficient (K D (PAR)), and chl-a/TN. Each statistical model consists of a sum of nonlinear functions to generate flow-adjusted time series and compute long-term trends accounting for climate effects on hydrology. We present results identifying successive periods of (1) eutrophication ca. 1945–1980 characterized by approximately doubled TN and NO2?+?NO3 loadings, leading to increased chl-a and associated ecosystem impairments, and (2) modest decreases of TN and NO2?+?NO3 loadings from 1981 to 2012, signaling a partial reversal of nutrient over-enrichment. Comparison of our findings with long-term trends of water-quality properties for a variety of estuarine and coastal ecosystems around the world reveals that trends for Chesapeake Bay are weaker than for other systems subject to strenuous management efforts, suggesting that more aggressive actions than those undertaken to date will be required to counter anthropogenic eutrophication of this valuable resource. 相似文献
4.
Transparent exopolymer particle (TEP) distributions were examined in North Carolina’s Neuse River Estuary (NRE) over a 1-year
period, and experiments were conducted to examine controls upon TEP formation. TEP-carbon averaged 16% of the total organic
carbon pool in the NRE. From May to early August 2007, TEP ranged from 805 to 1,801 μg xanthan gum (XG) L−1. A large phytoplankton bloom peaked in early August and then subsequently declined. Within 2 weeks of the bloom’s peak, TEP
concentrations increased to >3,500 μg XG L−1 and remained elevated through mid-December. Decreasing water temperatures and enhanced retention due to drought conditions
in Fall 2007 likely aided in the persistence of TEP concentrations during this timeframe. Thereafter, TEP decreased coincident
with increased river flow and flushing of the estuary that began in January 2008, and TEP remained low (ranging from 991 to
1,712 μg XG L−1) until the end of April 2008. TEP was positively correlated with salinity, suggesting that cation availability (which co-varies
with salinity and stabilizes the structural integrity of TEP) may play a role in estuarine TEP formation. In two cation addition
experiments using water from the mesohaline region, TEP concentrations tended to be higher in treatments with vs. without
cations added. Statistically significant relationships were also found between in situ TEP concentrations and pH, mixing,
and temperature, suggesting that a complex suite of environmental parameters affect TEP formation and its distribution in
estuaries. 相似文献
5.
Freshwater inputs often play a more direct role in estuarine phytoplankton biomass (chlorophyll a) accumulation than nitrogen (N) inputs, since discharge simultaneously controls both phytoplankton residence time and N loading. Understanding this link is critical, given potential changes in climate and human activities that may affect discharge and watershed N supply. Chlorophyll a (chla) relationships with hydrologic variability were examined in 3-year time series from two neighboring, shallow (<5?m), microtidal estuaries (New and Neuse River estuaries, NC, USA) influenced by the same climatic conditions and events. Under conditions ranging from drought to floods, N concentration and salinity showed direct positive and negative responses, respectively, to discharge for both estuaries. The response of chla to discharge was more complex, but was elucidated through conversion of discharge to freshwater flushing time, an estimate of transport time scale. Non-linear fits of chla to flushing time revealed non-monotonic, unimodal relationships that reflected the changing balance between intrinsic growth and losses through time and along the axis of each estuary. Maximum biomass occurred at approximately 10-day flushing times for both systems. Residual analysis of the fitted data revealed positive relationships between chla and temperature, suggesting enhanced growth rates at higher temperatures. N loading and system-wide, volume-weighted chla were positively correlated, and biomass yields per N load were greater than other marine systems. When combined with information on loss processes, these results on the hydrologic control of phytoplankton biomass will help formulate mechanistic models necessary to predict ecosystem responses to future climate and anthropogenic changes. 相似文献
6.
Bacterioplankton productivity (BP) spatial variation was investigated in relation to potential resources, including primary productivity and dissolved organic matter, in the micro-tidal Neuse River–Pamlico Sound estuarine system, North Carolina, USA. Estuarine BP was predicted to correlate with the trophic gradient, decreasing along the salinity gradient in parallel with the decrease in organic matter and primary productivity. This prediction was tested over four years at spatial scales ranging from kilometers to meters along the riverine axis and with depth. The general pattern of BP across the salinity gradient was unimodal and matched the phytoplankton patterns in peak location and variability. Peak locations varied with discharge, especially in 2003 when above average discharge moved peaks downstream. Spatial coherence of BP with other variables was much less at short time scales. The effect of temperature, nutrients, and phytoplankton on BP varied by location, especially fresh versus brackish stations, although only temperature explained more than 20% of the BP variation. Depth variation of BP was as great as longitudinal variation and bottom samples were often higher than surface. BP was strongly correlated with particulate organic carbon at the pycnocline and bottom, highlighting the importance of particulate matter as a resource. Station-averaged BP and phytoplankton data corresponded well with two published meta-analyses, although the offset of the freshwater station suggested longitudinal differences in community composition or resource availability. 相似文献
7.
A S Kane M J Dykstra E J Noga R Reimschuessel A Baya C Driscoll H W Paerl J Landsberg 《Marine environmental research》2000,50(1-5):473-477
Lesions in estuarine finfish are associated with a variety of organisms including parasites and bacterial, viral, and fungal infectious agents. In addition, trauma, suboptimal water quality, and other abiotic stress factors may result in the loss of homeostasis. We have observed solitary ulcerative lesions on menhaden sampled from the Chesapeake Bay, Maryland, the Pimlico River, North Carolina, and the St. Johns River, Florida. Histologically, the lesions demonstrated a marked chronic inflammatory infiltrate and granulomas in response to fungal hyphae throughout large areas of exposed necrotic muscle. Gram-negative rod-shaped bacteria were also observed in the lesions, a common finding in ulcers of aquatic organisms. Similar observations in menhaden and other species have been described previously in the literature as ulcerative mycosis, mycotic granulomatosis, red spot disease, and epizootic ulcerative syndrome. Despite the many different known causes of fish lesions, the popular press and the scientific literature have recently emphasized Pfiesteria piscicida and other Pfiesteria-like dinoflagellates (and their bioactive compounds) as the primary causative agent for finfish lesions, particularly mycotic granulomatous ulcers in Atlantic menhaden. While some laboratory data suggest that Pfiesteria may play a role in field-observed lesions, much more cause-and-effect evidence is needed to determine the importance of other risk factors, both alone or and in combination with Pfiesteria. In order to better understand the etiology of lesion initiation and progression in estuarine finfish, accurate assessments of environmental conditions collected on appropriate temporal and spatial scales, and fish morphological indicators consistent with gross and histological pathologic terminology, should be used for reporting fish lesion observations and kills. Further, this outlook will help to avoid bias and may foster a broader perspective for examining the health of estuarine systems in general. 相似文献
8.
Estuarine Phytoplankton Responses to Hurricanes and Tropical Storms with Different Characteristics (Trajectory,Rainfall, Winds) 总被引：1，自引：0，他引：1
We examined the short-term (<1 month post-storm) impact of storms [Tropical Storm (TS) Helene in 2000, Hurricane (H) Isabel
in 2003, H Alex, Tropical Depression (TD) Bonnie and TS Charley in 2004] varying in their trajectory, wind and rainfall characteristics,
on water column structure, nutrients, and phytoplankton biomass in North Carolina’s Neuse R. Estuary (NRE). Data are presented
from two sampling programs, ModMon (biweekly) and FerryMon (measurements made every 3 min daily). Helene’s winds mixed the
previously stratified water column, delivering sediment-bound nutrients to the euphotic zone, and localized freshwater input
from Helene was also evident. Mean chlorophyll a concentrations in the mesohaline portion of the NRE, where N was strongly limiting before the storm (molar DIN:DIP < 1),
more than doubled after the storm. Unlike with Helene, the water column was well mixed before passage of Isabel, and nutrient
concentrations were high. As a result, minimal impact on phytoplankton biomass was detected despite Isabel’s high winds and
significant freshwater input. In fact, conditions became less favorable for phytoplankton growth after the storm. Alex was
fast moving and relatively small, but its winds were sufficient to mix the water column. Although data from ModMon suggest
that chlorophyll a was only slightly higher after passage of Alex, FerryMon detected an ephemeral bloom that was missed by ModMon. Overall,
these results suggest that relatively small tropical storms and hurricanes can lead to significant increases in phytoplankton
biomass. However, the phytoplankton response depends on both the characteristics of a particular storm and the physical–chemical
conditions of the water column before storm passage. Finally, the ephemeral bloom that developed as a result of Alex, the
strong response of phytoplankton in the mesohaline portion of the estuary to nutrient inputs, and their patchiness on several
other occasions suggests that storms may create “hot spots” for trophic transfer and biogeochemical dynamics in estuaries.
Adaptive sampling is necessary to capture these features and to fully understand the impact of perturbations such as storms
on estuarine ecosystem functioning. 相似文献
9.
Gabriel E Machovsky-Capuska David Priddel Philip HW Leong Peter Jones Nicholas Carlile Lesley Shannon 《新西兰海洋与淡水研究杂志》2016,50(3):418-432
It is widely believed that predators maximise their energy intake while foraging and consume prey that are nutritionally similar. We combined GPS data loggers, miniaturised cameras, dietary sampling and nutritional geometry to examine the nutritional variability in the prey and selected diet, and foraging performance, of the masked booby (Sula dactylatra tasmani), a wild carnivore and marine top predator. Data loggers also revealed no significant differences between sexes in the foraging performance of chick-rearing adults. Females provided more food to their chicks than the males and, regardless of the nutritional variability of prey consumed, both sexes showed similar amounts of protein and lipid in their diets. Miniaturised cameras combined with nutritional analysis of prey provided, for the first time, fine-scale detail of the amounts of macronutrients consumed in each plunge dive and the overall foraging trip. Our methodology could be considered for future studies that aim to contribute to the general understanding of the behavioural and physiological mechanisms and ecological and evolutionary significance of animal foraging (e.g. energy expenditure budgets and prey selection for self- and offspring-feeding that could lead to sex-specific foraging strategies). 相似文献
10.
J. Stephen Fries Rachel T. Noble Hans W. Paerl Gregory W. Characklis 《Estuaries and Coasts》2007,30(2):359-364
Monitoring of estuarine condition depends on water quality parameters that have significant and interpretable ecological effects
and can be assessed either in situ or via rapid laboratory techniques. Two commonly measured parameters are water column turbidity
(NTU) and total suspended solids (TSS). Under certain conditions, either of these measures could represent a proxy for runoff
and provide rapid, in situ measures to improve protection of the public by decreasing the time required to detect and monitor
associated effects (e.g., reduced water clarity and eutrophication). The Neuse River Estuary (NRE) has experienced a decline
in water quality due to anthropogenic inputs, including stormwater containing nutrient and particle loads. Water samples were
collected from the NRE during both dry weather and storm events over 16 mo across the entire estuarine gradient. Particle
size distributions, ratio of particulate organic carbon to nitrogen, chlorophylla (chla), TSS, and NTU were measured in each of these samples, with the data separated into regions based on salinity and depth of
sample collection. Particle analyses were directed at identifying suspensions dominated by phytoplankton, runoff particles,
or resuspended sediments. Particle size distributions for suspensions in Region I (all samples with salinity less than 2)
varied little during sampling, resulting in a robust NTU-TSS relationship. This relationship confirmed the usefulness of turbidity
as a measure of runoff and resuspension of recently deposited runoff in the upper NRE. Phytoplankton cells represented a majority
of the particles in Region II (surface samples with salinity greater than 2), based on the close relationship between chla and total particle volume in these samples. Suspensions of large, nearly uniform diameter particles, which are likely aggregates
and resuspended sediment, were observed in Region III (bottom samples with salinity greater than 2). Using these techniques
as part of routine monitoring, particle suspension measures in different hydrographic regions of an estuary provide evidence
useful for identifying the source and water quality consequences of particle suspensions (e.g., microbial contamination and
algal blooms). 相似文献