Magnitude Of Phytoplankton Blooms Research Articles

Spatial and temporal changes in chlorophyll-a concentrations in the River Thames basin, UK: Are phosphorus concentrations beginning to limit phytoplankton biomass?

Chlorophyll-a and nutrient concentrations were monitored at weekly intervals across 21 river sites throughout the River Thames basin, southern England, between 2009 and 2011. Despite a 90% decrease in soluble reactive phosphorus (SRP) concentration of the lower River Thames since the 1990s, very large phytoplankton blooms still occur. Chlorophyll concentrations were highest in the mid and lower River Thames and the larger tributaries. Lowest chlorophyll concentrations were observed in the smaller tributaries, despite some having very high phosphorus concentrations of over 300μgl−1. There was a strong positive correlation between river length and mean chlorophyll concentration (R2=0.82), and rivers connected to canals had ca. six times greater chlorophyll concentration than ‘natural’ rivers with similar phosphorus concentrations, indicating the importance that residence time has on determining phytoplankton biomass. Phosphorus concentration did have some influence, with phosphorus-enriched rivers having much larger phytoplankton blooms than nutrient-poor rivers of a similar length. Water quality improvements may now be capping chlorophyll peaks in the Rivers Thames and Kennet, due to SRP depletion during the spring/early summer phytoplankton bloom period. Dissolved reactive silicon was also depleted to potentially-limiting concentrations for diatom growth in the River Thames during these phytoplankton blooms, but nitrate remained in excess for all rivers throughout the study period. Other potential mitigation measures, such as increasing riparian shading and reducing residence times by removing impoundments may be needed, alongside phosphorus mitigation, to reduce the magnitude of phytoplankton blooms in the future.

Control of primary production in the Arctic by nutrients and light: insights from a high resolution ocean general circulation model

Abstract. Until recently, the Arctic Basin was generally considered to be a low productivity area and was afforded little attention in global- or even basin-scale ecosystem modelling studies. Due to anthropogenic climate change however, the sea ice cover of the Arctic Ocean is undergoing an unexpectedly fast retreat, exposing increasingly large areas of the basin to sunlight. As indicated by existing Arctic phenomena such as ice-edge blooms, this decline in sea-ice is liable to encourage pronounced growth of phytoplankton in summer and poses pressing questions concerning the future of Arctic ecosystems. It thus provides a strong impetus to modelling of this region. The Arctic Ocean is an area where plankton productivity is heavily influenced by physical factors. As these factors are strongly responding to climate change, we analyse here the results from simulations of the 1/4° resolution global ocean NEMO (Nucleus for European Modelling of the Ocean) model coupled with the MEDUSA (Model for Ecosystem Dynamics, carbon Utilisation, Sequestration and Acidification) biogeochemical model, with a particular focus on the Arctic basin. Simulated productivity is consistent with the limited observations for the Arctic, with significant production occurring both under the sea-ice and at the thermocline, locations that are difficult to sample in the field. Results also indicate that a substantial fraction of the variability in Arctic primary production can be explained by two key physical factors: (i) the maximum penetration of winter mixing, which determines the amount of nutrients available for summer primary production, and (ii) short-wave radiation at the ocean surface, which controls the magnitude of phytoplankton blooms. A strong empirical correlation was found in the model output between primary production and these two factors, highlighting the importance of physical processes in the Arctic Ocean.

The impact of changing climate on phenology, productivity, and benthic–pelagic coupling in Narragansett Bay

The timing and magnitude of phytoplankton blooms have changed markedly in Narragansett Bay, RI (USA) over the last half century. The traditional winter–spring bloom has decreased or, in many years, disappeared. Relatively short, often intense, diatom blooms have become common in spring, summer, and fall replacing the summer flagellate blooms of the past. The annual and summer mean abundance (cell counts) and biomass (chl a) of phytoplankton appear to have decreased based on almost 50 years of biweekly monitoring by others at a mid bay station. These changes have been related to warming of the water, especially during winter, and to increased cloudiness. A significant decline in the winter wind speed may also have played a role. The changes in the phenology of the phytoplankton and the oligotrophication of the bay appear to have decreased greatly the quantity and (perhaps) quality of the organic matter being deposited on the bottom of the bay. This decline has resulted in a very much reduced benthic metabolism as reflected in oxygen uptake, nutrient regeneration, and the magnitude and direction of the net flux of N 2 gas. Based on many decades of standard weekly trawls carried out by the Graduate School of Oceanography, the winter biomass of bottom feeding epibenthic animals has also declined sharply at the mid bay station. After decades of relatively constant anthropogenic nitrogen loading (and declining phosphorus loading), the fertilization of the bay will soon be reduced during May–October due to implementation of advanced wastewater treatment. This is intended to produce an oligotrophication of the urban Providence River estuary and the Upper Bay. The anticipated decline in the productivity of the upper bay region will probably decrease summer hypoxia in that area. However, it may have unanticipated consequences for secondary production in the mid and lower bay where climate-induced oligotrophication has already much weakened the historically strong benthic–pelagic coupling.

Distant riverine nutrient supply and local temperature drive the long-term phytoplankton development in a temperate coastal basin

Since 1984, salinity, temperature, phytoplankton biomass and nutrients have been monitored in the List Tidal Basin (northern Wadden Sea, Europe). Nutrient dynamics follow a clear seasonal pattern with high winter concentrations and low summer concentrations. Interannual phytoplankton dynamics in the basin apparently responded to both decreasing riverine nutrient loads and the prevailing temperature regime. The mean spring diatom biomass (as Chlorophyll a) was correlated with temperature and the highest biomass was reached after cold winters. Summer phytoplankton (May–September) gradually decreased and correlated with Total Nitrogen loads from the rivers Weser and Elbe debouching about 150 km south of the List Tidal Basin into the North Sea. During summer, the frequency of observations with low nitrate concentrations (< 0.5 µM) significantly increased. We conclude that the long-term development of the phytoplankton is driven by a combination of riverine nitrogen loads and temperature. We expect that global warming and decreasing nutrient loads will reduce the magnitude of phytoplankton blooms in the List Tidal Basin.

Ocean Color Reveals Increased Blooms in Various Parts of the World

The magnitude of phytoplankton blooms has increased significantly in many areas of the world during the past 11 years, as shown in data from ocean color sensors on board satellites. These areas with increased blooms are likely to be environmentally stressed and undergoing undesirable environmental changes such as a higher frequency of harmful algal blooms and oxygen depletion in bottom layers of oceans, estuaries, and lakes. These changes can disrupt traditional fisheries and recreational use in many coastal areas.An algal bloom is a rapid increase in the concentration of phytoplankton algae that occurs when conditions turn favorable for algal growth. A typical example of a bloom is the phytoplankton spring bloom. Algal blooms are natural phenomena that remove dissolved carbon and nutrients. In addition, they produce new biomass that supports higher trophic levels including fish and fisheries. However, the blooms also lead to excessive turbidity, oxygen depletion in the bottom layers, and the possible death of fish, benthic animals, and bottom vegetation.

Variability in the freshwater balance of northern Marguerite Bay, Antarctic Peninsula: Results from δ18O

Abstract We investigate the seasonal variability in freshwater inputs to the Marguerite Bay region (Western Antarctic Peninsula) using a time series of oxygen isotopes in seawater from samples collected in the upper mixed layer of the ocean during 2002 and 2003. We find that meteoric water, mostly in the form of glacial ice melt, is the dominant freshwater source, accounting for up to 5% of the near-surface ocean during the austral summer. Sea-ice melt accounts for a much smaller percentage, even during the summer (maximum around 1%). The seasonality in meteoric water input to the ocean (around 2% of the near-surface ocean) is not dissimilar to that of sea-ice melt (around 2% in 2002 and 1% in 2003), contradicting the assumption that sea-ice processes dominate the seasonal evolution of the physical ocean environment close to the Antarctic continent. Three full-depth profiles of oxygen isotopes collected in successive Decembers (2001–2003) indicate that around 4 m of meteoric water is present in the water column at this time of year, and around 1 m of sea-ice formed from this same water column. The predominance of glacial melt is significant, since it is known to be an important factor in the operation of the ecosystem, for example by providing a source of nutrients and modifying the physical environment to control the spatial extent and magnitude of phytoplankton blooms. The Western Antarctic Peninsula is undergoing a very rapid change in climate, with increasing ocean and air temperatures, retreating glaciers, and increases in precipitation associated with changes in atmospheric circulation. As climate change continues, we expect meteoric water inputs to the adjacent ocean to rise further. Sea-ice in this sector of the Antarctic has shown a climatic decrease, and we expect a reduction in oceanic sea-ice melt fractions if this change continues. Continued monitoring of the oceanic freshwater budget at the western Peninsula is needed to track these changes as they occur, and to better understand their ecological consequences.

Ice-associated phytoplankton blooms in the southeastern Bering Sea

[1] Ice-associated phytoplankton blooms in the southeastern Bering Sea can critically impact the food web structure, from lower tropic level production to marine fisheries. By coupling pelagic and sea ice algal components, our 1-D ecosystem model successfully reproduced the observed ice-associated blooms in 1997 and 1999 at the NOAA/PMEL mooring M2. The model results suggest that the ice-associated blooms were seeded by sea ice algae released from melting sea ice. For an ice-associated bloom to grow and reach the typical magnitude of phytoplankton bloom in the region, ice melting-resulted low-salinity stratification must not be followed by a strong mixing event that would destroy the stratification. The ice-associated blooms had little impacts on the annual primary production, but had significant impacts in terms of shifting phytoplankton species, and the timing and magnitude of the bloom. These changes, superimposed on a gradual ecosystem shift attributed to global warming, can dramatically alter the Bering Sea ecosystem.

Vertical mixing effects on the phytoplankton bloom in the southeastern Bering Sea midshelf

A vertically one‐dimensional ecosystem model was developed and applied to the southeastern Bering Sea middle shelf. The physical model includes a 2.5‐level turbulence model. Tidal forcing was introduced to improve representation of tidal mixing in addition to wind stirring and thermal stratification. The simulated currents, thermocline and mixed‐layer depth (MLD) agree well with observations. The biological model was adapted from Eslinger et al. (2001) with nine compartments. The onset, magnitude and duration of the spring phytoplankton blooms were realistically reproduced at 12 m, 24 m, and 44 m in the standard run. The spring phytoplankton bloom was dominated by diatoms, and the post blooms by flagellates, which agree with previous studies in the region. The peak phytoplankton biomass reached 8 mmol N m−3, or approximately 16 mg Chl m−3, comparable to that observed in the PROBES program in 1980 and 1981 (Eslinger and Iverson, 2001). The simulated primary productions were within the range of 60 to 200 g C m−2/yr estimated in previous studies. Sensitivity studies revealed distinct effects of tidal mixing, wind stirring, thermal stratification and their impacts on the timing and magnitude of the phytoplankton bloom and the gross and net primary production. Links of MLD with primary production and species were found. If a constant MLD is used in the model, there exists a maximum gross primary production (GPP) at MLD = 24 m. Model results reveals that the predominant phytoplankton species changes from flagellates when MLD &lt; 15 m to diatoms when MLD &gt; 15 m.

Effect of El Nĩno on demographic, morphological, and chemical parameters in turtle-grass (Thalassia testudinum): an unexpected test of indicators.

We examined the response of demographic, morphological, and chemical parameters of turtle grass (Thalassia testudinum), to much-higher-than-normal rainfall associated with an El Niño event in the winter of 1997-1998. Up to 20 inches of added rain fell between December 1997 and March 1998. triggering widespread and persistent phytoplankton blooms along the west coast of Florida. Water-column chlorophyll concentrations estimated from serial Sea WiFS imagery were much higher during the El Niño event than in the previous or following years, although the timing and magnitude of phytoplankton blooms varied among sites. Seagrass samples collected in 1997, 1998, and 1999 provided an excellent opportunity to test the responsiveness of Thalassia to decline and subsequent improvement of water quality and clarity in four estuaries. Using a scoring technique based on temporal responsiveness, spatial consistency, and statistical strength of indicators, we found that several morphological parameters (Thalassia shoot density, blade width, blade number, and shoot-specific leaf area) were responsive and consistent measures of light stress. Some morphological parameters, such as rhizome apex density, responded to declines and subsequent improvement in water clarity, but lacked the statistical discriminating power necessary to be useful indicators. However, rhizome sugar, starch, and total carbohydrate concentrations also exhibited spatially and temporally consistent variation as well as statistical strength. Because changes in shoot density, as well as water clarity, affect rhizome carbohydrate levels, a composite metric based on Thalassia shoot density and rhizome carbohydrate levels together is probably more useful than either parameter alone as an indicator of seagrass health.

Iron, nutrient, and phytoplankton distributions in Oregon coastal waters

The relationship between iron and nitrate concentrations was examined off the coast of Oregon during the upwelling season. Surface Fe and N (nitrate + nitrite) concentrations measured underway by flow injection analysis ranged from &lt;0.3 to 20 nmol L−1 and &lt;0.1 to 30 μmol L−1, respectively. Total dissolvable Fe concentrations, measured in unfiltered, acidified samples in surface waters and in vertical profiles, ranged from &lt;0.3 to 300 nmol L−1. Surface water Fe and N concentrations were highly variable and uncoupled. Our observations indicate two dominant sources of Fe to Oregon coastal waters: Slope or shelf sediments and the Columbia River. Sedimentary iron, probably largely in the particulate form, appears to be added to surface waters through wind‐induced vertical mixing during strong winds, through thickening of the bottom mixed layer during relaxation or downwelling favorable wind conditions, and through outcropping of shelf bottom waters during upwelling events. The existence of multiple iron sources and the generally high iron concentrations may explain why the distribution of phytoplankton, measured both remotely (by Sea‐viewing Wide Field‐of‐view Sensor) and underway (by in vivo fluorescence), appeared to be driven primarily by physical dynamics and was not strongly linked to the distribution of iron. Nevertheless, at some offshore stations where underway Fe concentrations were &lt;0.3 nmol L−1, underway measurements of the physiological state of phytoplankton by fast repetition rate fluorometry were consistent with mild iron stress, and cross‐shelf nutrient distributions were consistent with iron regulation of the magnitude of phytoplankton blooms.

Impact of the Spring 2000 phytoplankton bloom in Chesapeake Bay on optical properties and light penetration in the Rhode River, Maryland

Accelerating eutrophication manifest as increasing frequency and magnitude of phytoplankton blooms threatens living resources in many estuaries. Effects of large blooms can be difficult to document because blooms are often unexpected and do not always coincide with scheduled sampling programs. Here we use continuously monitored salinity distributions and optical properties to study the spring bloom of the red tide dinoflagellate,Prorocentrumminimum, in the Rhode River, Maryland, a tributary embayment of upper Chesapeake Bay. Salinity distributions, together with weekly cruise measurements of nutrient concentrations, indicate that the bloom commenced with an influx of nitrate at the mouth due to the arrival of a freshet from the Susquehanna River. Arrival of this freshet at the mouth set up an unstable, inverse salinity gradient within the Rhode River. Continuously monitored absorption and scattering spectra indicated that increases in chlorophyll within the Rhode River initially were due to the influx of chlorophyll that had developed in the main stem of the bay. After the influx, much higher concentrations and steep spatial gradients developed within the Rhode River, subsequent to reduced mixing that accompanied re-establishment of a normal estuarine salinity gradient. We used the monitored absorption and scattering coefficients to determine the effect of the bloom on light attenuation coefficients in the Rhode River. The bloom resulted in a nearly three-fold increase in attenuation coefficient. Attenuation was dominated by chlorophyll in the early stages of the bloom and by detritus after the termination of the bloom. Although the bloom lasted only 20 d, the elevated attenuation coefficients due to the bloom exceeded values that would permit growth of submersed vascular plants for a period of about 45 d.

Impact of phytoplankton bloom magnitude on a pelagic microbial food web

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 144:211-221 (1996) - doi:10.3354/meps144211 Impact of phytoplankton bloom magnitude on a pelagic microbial food web Brussaard CPD, Gast GJ, van Duyl FC, Riegman R The impact of phytoplankton bloom magnitude on the microbial food web of the Dutch pelagic coastal zone (Southern Bight of the North Sea) was studied during spring 1993. Data were compared to a study carried out in 1992 at the same location. Light availability and temperature were the key factors for the timing of the diatom spring bloom. Specific algal cell lysis rates during the diatom bloom were always <0.1 d-1. Due to sinking of the diatoms no effect of the difference in bloom magnitude between the 2 years on the pelagic microbial food web was detected. A high onset level of nitrate (55 µM) resulted in a dense bloom of the colonial Phaeocystis, with maximum cell numbers of 1.8 x 108 cells l-1. During the development of the bloom, the pH of the seawater increased from 7.9 to 8.7. The bloom of Phaeocystis declined through cell lysis (up to 0.3 d-1). Due to the enhanced biomass of Phaeocystis the amounts of released algal cellular carbon were high (up to 400 µg C l-1 d-1). Differences in Phaeocystis bloom magnitude were, as a consequence of algal cell lysis, reflected in bacterial production (up to 90 µg C l-1 d-1 in 1993) and grazing activity of members of the microbial food web. The elevated importance of the microbial food web resulted in a high standing stock of microzooplankton (850 µg C l-1) and accumulation of regenerated inorganic nutrients. Calculations on both carbon and nitrogen budgets indicate that most of the Phaeocystis bloom was mineralized within the water column. Phytoplankton bloom magnitude · Diatoms · Phaeocystis · Cell lysis · Bacterial production · Microbial food web · Mineralization Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 144. Publication date: December 05, 1996 Print ISSN:0171-8630; Online ISSN:1616-1599 Copyright © 1996 Inter-Research.