Long-term variations in primary production in a eutrophic sub-estuary. II. Interannual variations and modeling

Gallegos, Charles L.

doi:10.3354/meps10713

Cited by 7 publications

(10 citation statements)

References 57 publications

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“…4B). The effect of these large blooms on deviations from the mean seasonal pattern of production and their contribution to interannual variation in annual production are analyzed elsewhere (Gallegos 2014).…”

Section: Seasonal Variabilitymentioning

confidence: 99%

Long-term variations in primary production in a eutrophic sub-estuary. I. Seasonal and spatial patterns

Gallegos¹

2014

Mar. Ecol. Prog. Ser.

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Daily rates of phytoplankton primary production were calculated from measurements of light saturation curves of photosynthesis for 20 yr at 6 stations on the Rhode River, Maryland (USA). Daily production, corrected for the geometry and spectrum of the underwater light field, averaged 1319 (range 1.4 to 15 800) mg C m. Log-transformation of the exact solution for depthintegrated daily production permitted linear analysis of seasonal and spatial patterns in production and the factors that determine it. The seasonal signal was the greatest source of variation, followed by spatial then interannual. The seasonal pattern was driven by coinciding summer maxima in both the chlorophyll a (chl a) biomass, B, and the light saturated photosynthetic rate normalized to chl a, P B max . The spatial pattern was characterized by a region in which production was relatively constant despite declining depth, a station at which production was reduced by truncation of the depth profile of production, and an area where mean production was lowest but variance was highest, due to local flow causing either localized blooms or washout of biomass and high turbidity at the station furthest up the estuary. Analysis of the components contributing to the variance in production indicated that variance in B and P B max added nearly equally to it. Covariance between B and the light attenuation coefficient reduced the variance in production. The analytical approach adopted here allowed these patterns to be discerned against a high degree of overall variability, and should be similarly useful in a wide range of systems.

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Section: Seasonal Variabilitymentioning

confidence: 99%

Long-term variations in primary production in a eutrophic sub-estuary. I. Seasonal and spatial patterns

Gallegos¹

2014

Mar. Ecol. Prog. Ser.

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“…Additionally, variation in PAR transparency is an important predictor of both short and long‐term variation in phytoplankton production in the mesohaline Rhode River sub‐estuary of the Chesapeake Bay (Fig. ; Gallegos, , b ; Gallegos and Neale, ). The diffuse attenuation coefficient of PAR ( K d PAR) in the Chesapeake Bay and its tributaries has traditionally been modeled as a simple function of water quality variables (Xu et al ).…”

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confidence: 99%

Patterns of spectral, spatial, and long‐term variability in light attenuation in an optically complex sub‐estuary

Rose

Neale

Tzortziou

et al. 2018

Limnology & Oceanography

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The attenuation of solar radiation controls many processes and characteristics of aquatic ecosystems and is a sentinel of larger-scale environmental change. While light attenuation is often characterized with a single broadband diffuse attenuation coefficient of photosynthetically active radiation (K d PAR), attenuation can exhibit substantial variability across the solar spectrum and through time and space. Understanding this variability and its proximate causes may provide information to characterize large-scale environmental change. We implemented a semi-analytical K d model in four segments of the Rhode River sub-estuary of the Chesapeake Bay to examine spectral, spatial, and temporal variability in K d across the ultraviolet (UV) to PAR wavelengths (290-710 nm) over the period 1986-2014. We used this model to identify wavelengths most sensitive to long-term change, the seasonal phenology of long-term change, and the optical constituents driving changes. The model included contributions by phytoplankton, non-algal particulates, chromophoric dissolved organic matter (CDOM), and water. Over the period of record, K d increased (water transparency decreased) in both UV and PAR wavelengths, with the largest increases at the most upstream site, during summer months, and at short UV wavelengths. These increases were due primarily to an increase in non-algal particulates, and particularly since year 2005, however there was substantial seasonality in K d . The model reveals how different changes in water quality have a differential effect on UV and PAR attenuation, and enables insight into what types of long-term change in transparency have occurred over the long period of human impacts in the Chesapeake Bay watershed.

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“…One of the best-studied ecosystems in the survey was the Rhode River, a small sub-estuary adjacent to the MH salinity zone of Chesapeake Bay. Long-term measurements of photosynthesis by Gallegos 63 supported estimates of APPP ranging from 152 to 612 g C m −1 y −1 in the Rhode River, with a mean of 328 g C m −1 y −1 . APPP maxima occurred in years with dense spring blooms of Prorocentrum cordatum (formerly P. minimum) a dinoflagellate species that commonly forms "mahogany tides".…”

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confidence: 76%

Seasonal to Inter-Annual Variability of Primary Production in Chesapeake Bay: Prospects to Reverse Eutrophication and Change Trophic Classification

Harding

Mallonee

Perry

et al. 2020

Sci Rep

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estuarine-coastal ecosystems are rich areas of the global ocean with elevated rates of organic matter production supporting major fisheries. Net and gross primary production (NPP, GPP) are essential properties of these ecosystems, characterized by high spatial, seasonal, and inter-annual variability associated with climatic effects on hydrology. Over 20 years ago, Nixon defined the trophic classification of marine ecosystems based on annual phytoplankton primary production (APPP), with categories ranging from "oligotrophic" to "hypertrophic". Source data consisting of shipboard measurements of NPP and GPP from 1982 to 2004 for Chesapeake Bay in the mid-Atlantic region of the United States supported estimates of APPP from 300 to 500 g C m −2 yr −1 , corresponding to "eutrophic" to "hypertrophic" categories. Here, we developed generalized additive models (GAM) to interpolate the limited spatio-temporal resolution of source data. Principal goals were: (1) to develop predictive models of NPP and GPP calibrated to source data (1982 to 2004); (2) to apply the models to historical (1960s, 1970s) and monitoring (1985 to 2015) data with adjustments for nutrient loadings and climatic effects; (3) to estimate APPP from model predictions of NPP; (4) to test effects of simulated reductions of phytoplankton biomass or nutrient loadings on trophic classification based on APPP. Simulated 40% decreases of euphotic-layer chl-a or tn and no 2 + no 3 loadings led to decreasing APPP sufficient to change trophic classification from "eutrophic' to "mesotrophic" for oligohaline (OH) and polyhaline (PH) salinity zones, and from "hypertrophic" to "eutrophic" for the mesohaline (MH) salinity zone of the bay. These findings show that improved water quality is attainable with sustained reversal of nutrient overenrichment sufficient to decrease phytoplankton biomass and APPP. Annual phytoplankton primary production (APPP) accounts for ~50 petagrams (=50 × 10 12 kg) of net primary production (NPP) in the oceans each year, half the global total for oceanic and terrestrial ecosystems according to a comprehensive review by Chavez et al. 1. Among ocean provinces, estuarine-coastal ecosystems have been characterized as biogeochemical "hot spots" by Cloern et al. 2 based on high contributions to APPP. In 1995, Nixon 3 classified marine ecosystems as "oligotrophic" to "hypertrophic" based on APPP, with several estuaries in the mid-Atlantic region of the United States ranking toward the high end of the range (Fig. 1). Important advances

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Long-term variations in primary production in a eutrophic sub-estuary. II. Interannual variations and modeling

Cited by 7 publications

References 57 publications

Long-term variations in primary production in a eutrophic sub-estuary. I. Seasonal and spatial patterns

Long-term variations in primary production in a eutrophic sub-estuary. I. Seasonal and spatial patterns

Patterns of spectral, spatial, and long‐term variability in light attenuation in an optically complex sub‐estuary

Seasonal to Inter-Annual Variability of Primary Production in Chesapeake Bay: Prospects to Reverse Eutrophication and Change Trophic Classification

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