The hypothesis that sediment organic content is limiting growth and distribution of the seagrass ... more The hypothesis that sediment organic content is limiting growth and distribution of the seagrass Zostera marina was tested in Chincoteague Bay, Maryland, and in a controlled mesocosm experiment. In the field, Z. marina was usually absent from areas with sediment organic content > 4%, especially compared with areas with sediment organic content < 4%. In contrast, in a mesocosm experiment, Z. marina thrived in organic rich (4 to 6%) sediment, developing long leaves and disproportionately short roots. Such plants have high drag and low anchoring capacity. As a result, Z. marina plants grown in organic rich sediment are more likely to be dislodged than are plants grown in organic poor sand. We hypothesize that when organic rich sediments are found in hydrodynamically active areas, a mismatch occurs between plant morphology and the physical environment, leading to the loss of seagrasses due to uprooting. Therefore, sediment organic content limitations in seagrass habitats need to be evaluated within the local hydrodynamic settings. Fine organic sediment may be less limiting to seagrasses in quiescent waters while sand with low organic content may be required for seagrass survival in hydrodynamically active areas.
Field-based, hands-on experiential learning is a mainstay of meaningful environmental science edu... more Field-based, hands-on experiential learning is a mainstay of meaningful environmental science education throughout a student's school career. Engaging K-12 students in field-based, experiential learning can help develop true passion and commitment to STEM (Science, Technology, Engineering, Math) subjects, allowing students to apply their skills and content knowledge in an authentic, experiential context while enhancing many academic skills and engaging them in contextualized learning across disciplines. To develop an environmentally literate population, and to solve the increasingly complex environmental issues facing society, there is a need to increase students' access to environmental education field experiences and to connect these outdoor experiences to relevant curricula within the classroom. This is especially important in urban environments, where citizens and students may be less connected on a day-today basis with nature. Examples of programs in two regions that model this approach are the Billion Oyster Project-Curriculum and Community Enterprise for Restoration Science STEM-C-Project (STEM, plus computing), in New York City, and the combined efforts of the Maryland Environmental Literacy Partnership (MELP) and the NOAA Bay-Watershed Education and Training (B-WET) program, both of which focus on the Chesapeake Bay, its watershed, and Baltimore Harbor. Both regions have invested in education programs that take advantage of their harbor/waterway locations and their maritime cultures and histories. The NYC program centers around 'Oyster Restoration Stations' visited by middle-school students and citizen scientists, who use a common set of protocols and a matching digital platform interface to record data including water quality and oyster biology. The Chesapeake programs, utilize both public and private partnerships to support teachers in designing inquiry-based field investigations to support curriculum underpinning the nation's first state mandated environmental literacy requirement for high school graduation. These two regional programs provide models for implementing experiential hands-on learning in environmental science and ecology for other urban areas.
Rates of photosynthesis and nitrogen fixation were measured along with species composition and pl... more Rates of photosynthesis and nitrogen fixation were measured along with species composition and plankton biomass during cyanobacteria blooms in the upper Sassafras River, a poorly buffered tidal freshwater tributary of Chesapeake Bay, USA. The mixed species composition of the cyanobacteria consortium appears to allow these species to take advantage of temporal variations in dissolved inorganic carbon (DIC) and dissolved oxygen (DO) to fix carbon (C) and nitrogen (N) under conditions limiting to most phytoplankton. At the early stage of the bloom, diazotrophic (nitrogen fixing) cyanobacteria species became dominant, likely as a consequence of nitrogen limitation; both rates of N 2-fixer biomass-normalized N 2 fixation and chlorophyll a-based photosynthesis increased with irradiance during this bloom stage. When the bloom reached peak biomass, photosynthetic carbon uptake and oxygen production resulted in DIC depletion and oxygen oversaturation. The constraint of oxygen on nitrogenase activity and concomitant C limitation on photosynthesis caused inhibition of N 2 fixation in the light during bloom peaks. N 2 fixation in the dark period accounted for ~40% of daily N 2 fixation when pH and DO were extremely high, and cyanobacteria species known to fix N 2 in the dark were dominant in the consortium at these times. The presence of cyanobacteria species with different environmental tolerances resulted in bloom persistence under limiting conditions for most eukaryotic phytoplankton. N 2 fixation by cyanobacteria consortia is an important component of the nitrogen cycle in some oligohaline and tidal freshwater estuaries.
Aquatic Microbial Ecology and Biogeochemistry: A Dual Perspective, 2016
Blooms of the toxic cyanobacterium, Lyngbya majuscula, were observed in Moreton Bay, Australia, b... more Blooms of the toxic cyanobacterium, Lyngbya majuscula, were observed in Moreton Bay, Australia, beginning in the late 1990s. These dense blooms led to significant human and ecosystem health impacts. Research on the causes of the bloom focused on nutrient interactions (e.g., nitrogen, phosphorus, and iron) and light availability, in particular, light quality. Light quality investigations reported here were instigated because of the abundance of humic-stained water runoff from the catchment that periodically washed into the primary bloom locations. Light quality experiments were conducted on L. majuscula in aquaria using spectral filters to simulate different light regimes. The most pronounced effect on L. majuscula pigment content and productivity rates was the colored water treatment that simulated the humic-stained runoff. Colored water stimulated pigment content (phycoerythrin and chlorophyll a) and productivity (14C uptake) compared with clear water, turbid water, and a combination of turbid/colored water treatments. Previous research identified the importance of humic compounds in making iron bioavailable to L. majuscula. These results, combined with previous studies of L. majuscula and nutrient interactions, were used to construct a conceptual model of the primary causes of L. majuscula blooms in Moreton Bay, Australia. This model is presented in a diagrammatic format to synthesize research results as to the causes of these cyanobacteria blooms. The Lyngbya majuscula model focuses on having sufficient nutrients, particularly bioavailable iron, in a light climate of colored water. This model for toxic cyanobacteria blooms of L. majuscula in Australia also has relevance in other parts of the world.
This study represents the most comprehensive assessment of kinetic parameters for Karenia brevis ... more This study represents the most comprehensive assessment of kinetic parameters for Karenia brevis to date as it encompasses natural populations sampled during three different bloom years in addition to cultured strains under controlled conditions. Nitrogen (N) uptake kinetics for ammonium (NH 4 +), nitrate (NO 3 À), urea, an amino acid mixture, individual amino acids (glutamate and alanine), and humic substrates were examined for the toxic red tide dinoflagellate, K. brevis, during short term incubations (0.5-1 h) using 15 N tracer techniques. Experiments were conducted using natural populations collected during extensive blooms along the West Florida Shelf in October 2001, 2002, and 2007, and in cultured strains (CCFWC 251 and CCFWC 267) obtained from the Florida Fish and Wildlife Institute culture collection. Kinetic parameters for the maximum uptake velocity (V max), half-saturation concentration (K s), and the affinity constant (a) were determined. The affinity constant is considered a more accurate indicator of substrate affinity at low concentrations. K. brevis took up all organic substrates tested, including N derived from humic substances. Uptake rates of the amino acid mixture and some NO 3 À incubations did not saturate even at the highest substrate additions (50-200 mmol N L À1). Based upon the calculated a values, the greatest substrate preference was for NH 4 + followed by NO 3 À ! urea, humic compounds and amino acids. The ability of K. brevis to utilize a variety of inorganic and organic substrates likely helps it flourish under a wide range of nutrient conditions from bloom initiation in oligotrophic waters offshore to bloom maintenance near shore where ambient nutrient concentrations may be orders of magnitude greater.
Abstract Blooms of Karenia brevis plague the West Florida Shelf (WFS) region in the Gulf of Mexic... more Abstract Blooms of Karenia brevis plague the West Florida Shelf (WFS) region in the Gulf of Mexico (GOM) where they exert harmful effects on aquatic biota and humans. Because productivity on the WFS is N limited, new N inputs into the region are thought to trigger blooms of K. brevis. Here we examine the potential for new N inputs via N2 fixation by Trichodesmium and other diazotrophic plankton to contribute to the N demand of K. brevis. Because of possible methodological biases, we also compared N2 fixation rates by cultured Trichodesmium using the 15N2 bubble addition method and the 15N2 saturated seawater. Both methods yielded identical results in 12 and 24 h incubations; however, there was more variability in rate estimates made using the bubble addition method. Pelagic N2 fixation rates by other planktonic diazotrophs ranged from 0 to 13.6 nmol N L−1 d−1, comparable to or higher than rates observed in oligotrophic gyres. These rates should be considered conservative estimates because they were made using the bubble addition method. Integrating over our study area, we estimate that new inputs of N to the WFS via N2 fixation are on the order of 0.011 Tmol N annually. Further, we measured directly the trophic transfer of recently fixed N2 to co-occurring plankton that included K. brevis and found that up to 47% of N2 fixed was transferred to non-diazotrophic plankton even in short (
... Large numbers of juvenile Macrosetella have also been found associated with Trichodesmium in ... more ... Large numbers of juvenile Macrosetella have also been found associated with Trichodesmium in waters off Japan (Tokioka & Bieri, 1966 ; Ohki ... the two dominant species of Trichodesmium, T thiebautii and T ery-thraeum by Macrosetella gracilis and Miracia effer-ata were also ...
Expansive blooms of the toxic cyanobacterium Lyngbya majuscula were observed in 2 shallow water r... more Expansive blooms of the toxic cyanobacterium Lyngbya majuscula were observed in 2 shallow water regions of Moreton Bay, Australia. The rapid bloom decline (8 to <1 km 2 in < 7 d) prompted an investigation of the role of cyanophage viruses in the ecophysiology of L. majuscula. Virus-like particles produced by decaying L. majuscula were observed using electron microscopy. The virus-like particles were similar in morphology to viruses in the genus Cyanostyloviridae. The effect of viruses on L. majuscula photosynthesis was investigated by: (1) creating a virus concentrate using tangential-flow ultrafiltration of seawater surrounding L. majuscula; (2) inoculating L. majuscula with the concentrate; and (3) measuring photosynthetic response using a pulse-amplitude modulated fluorometer. Virus concentrate addition resulted in decreased initial fluorescence, decreased photochemical efficiency and decreased electron transport rate in rapid light curves after 5 d. Viruses present within L. majuscula filaments may play an important role in the bloom dynamics of this ecologically important cyanobacterium.
O'Neil, JM, Albert, S., Osborne, N., Shaw, GR, Heil, CA, Mulholland, M. and Bronk, DA (2004)... more O'Neil, JM, Albert, S., Osborne, N., Shaw, GR, Heil, CA, Mulholland, M. and Bronk, DA (2004). Nitrogen acquisition by the toxic marine cyanobacterium Lyngbya majuscula from Moreton Bay Australia and Tampa Bay Florida. In: , Harmful Algae. XIth International Conference ...
... Brown and Boyd, 1982) and intoxication due to ingestion of sea-turtle meat and macroalgae epi... more ... Brown and Boyd, 1982) and intoxication due to ingestion of sea-turtle meat and macroalgae epiphytised by L. majuscula (Osborne et al ... wracks of decaying L. majuscula by local government for health and aesthetic reasons (Dennison and Abal, 1999 and O'Neil and Dennison ...
Limnol. Oceanogr., 51(5), 2006, 2484 E 2006, by the American Society of Limnology and Oceanograph... more Limnol. Oceanogr., 51(5), 2006, 2484 E 2006, by the American Society of Limnology and Oceanography, Inc. ... Erratum: Nitrogen fixation and release of fixed nitrogen by Trichodesmium spp. in the Gulf of Mexico ... There is an error in our paper published in L&O 51: ...
Summary Intensive sampling of the Maryland Coastal Bays in May and July of 2007 served to further... more Summary Intensive sampling of the Maryland Coastal Bays in May and July of 2007 served to further assess spatial patterns in nutrients, responses of biological indicators, seasons, land use, and nutrient cycling. Studies conducted in 2004 and 2006 had pinpointed the regions of St. Martin River and Johnsons Bay as areas of degraded water quality, high turbidity, increasing total nitrogen and phosphorus concentrations, high natural isotope abundance (δ15N), and low dissolved oxygen. Therefore the current study sought to ...
Harmful blooms of the benthic cyanobacteria Lyngbya spp. are increasing in coastal marine habitat... more Harmful blooms of the benthic cyanobacteria Lyngbya spp. are increasing in coastal marine habitats. Nutrient enrichment has been implicated in bloom formation; however, the effects of nutrient enrichment on secondary metabolite concentrations and the resulting palatability of Lyngbya spp. are not known. Using nutrient bioassays, we examined the effects of nitrogen (N), phosphorus (P) and chelated iron (Fe) on growth and secondary metabolite concentration in Lyngbya sp. collected from reefs in Broward County, Florida. The consequences of these nutrient additions on feeding behavior of a major specialist opisthobranch grazer, Stylocheilus striatus, were examined. Chelated Fe additions (+FeEDTA) significantly increased Lyngbya sp. growth, while additions of N, P and chelated Fe combined (+All) resulted in significantly lower concentrations of microcolin A than in the control. Overall, there was a negative correlation between growth and total concentrations of microcolins A and B. When crude extracts from the control, +FeEDTA and +All treatments of the Lyngbya sp. bioassay were offered to S. striatus in artificial food, they consumed greater quantities of the control and +FeEDTA treatments than the +All. These results provide the first evidence that changes in nutrient availability can affect secondary metabolite concentrations in marine Lyngbya spp. and support previous studies that show that Fe can stimulate growth in benthic marine cyanobacteria. This study also demonstrates quantifiable changes in feeding behavior by a specialist grazer in response to changes in the nutrient conditions under which Lyngbya sp. grows and underscores the need to consider secondary metabolite concentrations, and their effect on grazers, when managing harmful algal blooms.
The hypothesis that sediment organic content is limiting growth and distribution of the seagrass ... more The hypothesis that sediment organic content is limiting growth and distribution of the seagrass Zostera marina was tested in Chincoteague Bay, Maryland, and in a controlled mesocosm experiment. In the field, Z. marina was usually absent from areas with sediment organic content > 4%, especially compared with areas with sediment organic content < 4%. In contrast, in a mesocosm experiment, Z. marina thrived in organic rich (4 to 6%) sediment, developing long leaves and disproportionately short roots. Such plants have high drag and low anchoring capacity. As a result, Z. marina plants grown in organic rich sediment are more likely to be dislodged than are plants grown in organic poor sand. We hypothesize that when organic rich sediments are found in hydrodynamically active areas, a mismatch occurs between plant morphology and the physical environment, leading to the loss of seagrasses due to uprooting. Therefore, sediment organic content limitations in seagrass habitats need to be evaluated within the local hydrodynamic settings. Fine organic sediment may be less limiting to seagrasses in quiescent waters while sand with low organic content may be required for seagrass survival in hydrodynamically active areas.
Field-based, hands-on experiential learning is a mainstay of meaningful environmental science edu... more Field-based, hands-on experiential learning is a mainstay of meaningful environmental science education throughout a student's school career. Engaging K-12 students in field-based, experiential learning can help develop true passion and commitment to STEM (Science, Technology, Engineering, Math) subjects, allowing students to apply their skills and content knowledge in an authentic, experiential context while enhancing many academic skills and engaging them in contextualized learning across disciplines. To develop an environmentally literate population, and to solve the increasingly complex environmental issues facing society, there is a need to increase students' access to environmental education field experiences and to connect these outdoor experiences to relevant curricula within the classroom. This is especially important in urban environments, where citizens and students may be less connected on a day-today basis with nature. Examples of programs in two regions that model this approach are the Billion Oyster Project-Curriculum and Community Enterprise for Restoration Science STEM-C-Project (STEM, plus computing), in New York City, and the combined efforts of the Maryland Environmental Literacy Partnership (MELP) and the NOAA Bay-Watershed Education and Training (B-WET) program, both of which focus on the Chesapeake Bay, its watershed, and Baltimore Harbor. Both regions have invested in education programs that take advantage of their harbor/waterway locations and their maritime cultures and histories. The NYC program centers around 'Oyster Restoration Stations' visited by middle-school students and citizen scientists, who use a common set of protocols and a matching digital platform interface to record data including water quality and oyster biology. The Chesapeake programs, utilize both public and private partnerships to support teachers in designing inquiry-based field investigations to support curriculum underpinning the nation's first state mandated environmental literacy requirement for high school graduation. These two regional programs provide models for implementing experiential hands-on learning in environmental science and ecology for other urban areas.
Rates of photosynthesis and nitrogen fixation were measured along with species composition and pl... more Rates of photosynthesis and nitrogen fixation were measured along with species composition and plankton biomass during cyanobacteria blooms in the upper Sassafras River, a poorly buffered tidal freshwater tributary of Chesapeake Bay, USA. The mixed species composition of the cyanobacteria consortium appears to allow these species to take advantage of temporal variations in dissolved inorganic carbon (DIC) and dissolved oxygen (DO) to fix carbon (C) and nitrogen (N) under conditions limiting to most phytoplankton. At the early stage of the bloom, diazotrophic (nitrogen fixing) cyanobacteria species became dominant, likely as a consequence of nitrogen limitation; both rates of N 2-fixer biomass-normalized N 2 fixation and chlorophyll a-based photosynthesis increased with irradiance during this bloom stage. When the bloom reached peak biomass, photosynthetic carbon uptake and oxygen production resulted in DIC depletion and oxygen oversaturation. The constraint of oxygen on nitrogenase activity and concomitant C limitation on photosynthesis caused inhibition of N 2 fixation in the light during bloom peaks. N 2 fixation in the dark period accounted for ~40% of daily N 2 fixation when pH and DO were extremely high, and cyanobacteria species known to fix N 2 in the dark were dominant in the consortium at these times. The presence of cyanobacteria species with different environmental tolerances resulted in bloom persistence under limiting conditions for most eukaryotic phytoplankton. N 2 fixation by cyanobacteria consortia is an important component of the nitrogen cycle in some oligohaline and tidal freshwater estuaries.
Aquatic Microbial Ecology and Biogeochemistry: A Dual Perspective, 2016
Blooms of the toxic cyanobacterium, Lyngbya majuscula, were observed in Moreton Bay, Australia, b... more Blooms of the toxic cyanobacterium, Lyngbya majuscula, were observed in Moreton Bay, Australia, beginning in the late 1990s. These dense blooms led to significant human and ecosystem health impacts. Research on the causes of the bloom focused on nutrient interactions (e.g., nitrogen, phosphorus, and iron) and light availability, in particular, light quality. Light quality investigations reported here were instigated because of the abundance of humic-stained water runoff from the catchment that periodically washed into the primary bloom locations. Light quality experiments were conducted on L. majuscula in aquaria using spectral filters to simulate different light regimes. The most pronounced effect on L. majuscula pigment content and productivity rates was the colored water treatment that simulated the humic-stained runoff. Colored water stimulated pigment content (phycoerythrin and chlorophyll a) and productivity (14C uptake) compared with clear water, turbid water, and a combination of turbid/colored water treatments. Previous research identified the importance of humic compounds in making iron bioavailable to L. majuscula. These results, combined with previous studies of L. majuscula and nutrient interactions, were used to construct a conceptual model of the primary causes of L. majuscula blooms in Moreton Bay, Australia. This model is presented in a diagrammatic format to synthesize research results as to the causes of these cyanobacteria blooms. The Lyngbya majuscula model focuses on having sufficient nutrients, particularly bioavailable iron, in a light climate of colored water. This model for toxic cyanobacteria blooms of L. majuscula in Australia also has relevance in other parts of the world.
This study represents the most comprehensive assessment of kinetic parameters for Karenia brevis ... more This study represents the most comprehensive assessment of kinetic parameters for Karenia brevis to date as it encompasses natural populations sampled during three different bloom years in addition to cultured strains under controlled conditions. Nitrogen (N) uptake kinetics for ammonium (NH 4 +), nitrate (NO 3 À), urea, an amino acid mixture, individual amino acids (glutamate and alanine), and humic substrates were examined for the toxic red tide dinoflagellate, K. brevis, during short term incubations (0.5-1 h) using 15 N tracer techniques. Experiments were conducted using natural populations collected during extensive blooms along the West Florida Shelf in October 2001, 2002, and 2007, and in cultured strains (CCFWC 251 and CCFWC 267) obtained from the Florida Fish and Wildlife Institute culture collection. Kinetic parameters for the maximum uptake velocity (V max), half-saturation concentration (K s), and the affinity constant (a) were determined. The affinity constant is considered a more accurate indicator of substrate affinity at low concentrations. K. brevis took up all organic substrates tested, including N derived from humic substances. Uptake rates of the amino acid mixture and some NO 3 À incubations did not saturate even at the highest substrate additions (50-200 mmol N L À1). Based upon the calculated a values, the greatest substrate preference was for NH 4 + followed by NO 3 À ! urea, humic compounds and amino acids. The ability of K. brevis to utilize a variety of inorganic and organic substrates likely helps it flourish under a wide range of nutrient conditions from bloom initiation in oligotrophic waters offshore to bloom maintenance near shore where ambient nutrient concentrations may be orders of magnitude greater.
Abstract Blooms of Karenia brevis plague the West Florida Shelf (WFS) region in the Gulf of Mexic... more Abstract Blooms of Karenia brevis plague the West Florida Shelf (WFS) region in the Gulf of Mexico (GOM) where they exert harmful effects on aquatic biota and humans. Because productivity on the WFS is N limited, new N inputs into the region are thought to trigger blooms of K. brevis. Here we examine the potential for new N inputs via N2 fixation by Trichodesmium and other diazotrophic plankton to contribute to the N demand of K. brevis. Because of possible methodological biases, we also compared N2 fixation rates by cultured Trichodesmium using the 15N2 bubble addition method and the 15N2 saturated seawater. Both methods yielded identical results in 12 and 24 h incubations; however, there was more variability in rate estimates made using the bubble addition method. Pelagic N2 fixation rates by other planktonic diazotrophs ranged from 0 to 13.6 nmol N L−1 d−1, comparable to or higher than rates observed in oligotrophic gyres. These rates should be considered conservative estimates because they were made using the bubble addition method. Integrating over our study area, we estimate that new inputs of N to the WFS via N2 fixation are on the order of 0.011 Tmol N annually. Further, we measured directly the trophic transfer of recently fixed N2 to co-occurring plankton that included K. brevis and found that up to 47% of N2 fixed was transferred to non-diazotrophic plankton even in short (
... Large numbers of juvenile Macrosetella have also been found associated with Trichodesmium in ... more ... Large numbers of juvenile Macrosetella have also been found associated with Trichodesmium in waters off Japan (Tokioka & Bieri, 1966 ; Ohki ... the two dominant species of Trichodesmium, T thiebautii and T ery-thraeum by Macrosetella gracilis and Miracia effer-ata were also ...
Expansive blooms of the toxic cyanobacterium Lyngbya majuscula were observed in 2 shallow water r... more Expansive blooms of the toxic cyanobacterium Lyngbya majuscula were observed in 2 shallow water regions of Moreton Bay, Australia. The rapid bloom decline (8 to <1 km 2 in < 7 d) prompted an investigation of the role of cyanophage viruses in the ecophysiology of L. majuscula. Virus-like particles produced by decaying L. majuscula were observed using electron microscopy. The virus-like particles were similar in morphology to viruses in the genus Cyanostyloviridae. The effect of viruses on L. majuscula photosynthesis was investigated by: (1) creating a virus concentrate using tangential-flow ultrafiltration of seawater surrounding L. majuscula; (2) inoculating L. majuscula with the concentrate; and (3) measuring photosynthetic response using a pulse-amplitude modulated fluorometer. Virus concentrate addition resulted in decreased initial fluorescence, decreased photochemical efficiency and decreased electron transport rate in rapid light curves after 5 d. Viruses present within L. majuscula filaments may play an important role in the bloom dynamics of this ecologically important cyanobacterium.
O'Neil, JM, Albert, S., Osborne, N., Shaw, GR, Heil, CA, Mulholland, M. and Bronk, DA (2004)... more O'Neil, JM, Albert, S., Osborne, N., Shaw, GR, Heil, CA, Mulholland, M. and Bronk, DA (2004). Nitrogen acquisition by the toxic marine cyanobacterium Lyngbya majuscula from Moreton Bay Australia and Tampa Bay Florida. In: , Harmful Algae. XIth International Conference ...
... Brown and Boyd, 1982) and intoxication due to ingestion of sea-turtle meat and macroalgae epi... more ... Brown and Boyd, 1982) and intoxication due to ingestion of sea-turtle meat and macroalgae epiphytised by L. majuscula (Osborne et al ... wracks of decaying L. majuscula by local government for health and aesthetic reasons (Dennison and Abal, 1999 and O'Neil and Dennison ...
Limnol. Oceanogr., 51(5), 2006, 2484 E 2006, by the American Society of Limnology and Oceanograph... more Limnol. Oceanogr., 51(5), 2006, 2484 E 2006, by the American Society of Limnology and Oceanography, Inc. ... Erratum: Nitrogen fixation and release of fixed nitrogen by Trichodesmium spp. in the Gulf of Mexico ... There is an error in our paper published in L&O 51: ...
Summary Intensive sampling of the Maryland Coastal Bays in May and July of 2007 served to further... more Summary Intensive sampling of the Maryland Coastal Bays in May and July of 2007 served to further assess spatial patterns in nutrients, responses of biological indicators, seasons, land use, and nutrient cycling. Studies conducted in 2004 and 2006 had pinpointed the regions of St. Martin River and Johnsons Bay as areas of degraded water quality, high turbidity, increasing total nitrogen and phosphorus concentrations, high natural isotope abundance (δ15N), and low dissolved oxygen. Therefore the current study sought to ...
Harmful blooms of the benthic cyanobacteria Lyngbya spp. are increasing in coastal marine habitat... more Harmful blooms of the benthic cyanobacteria Lyngbya spp. are increasing in coastal marine habitats. Nutrient enrichment has been implicated in bloom formation; however, the effects of nutrient enrichment on secondary metabolite concentrations and the resulting palatability of Lyngbya spp. are not known. Using nutrient bioassays, we examined the effects of nitrogen (N), phosphorus (P) and chelated iron (Fe) on growth and secondary metabolite concentration in Lyngbya sp. collected from reefs in Broward County, Florida. The consequences of these nutrient additions on feeding behavior of a major specialist opisthobranch grazer, Stylocheilus striatus, were examined. Chelated Fe additions (+FeEDTA) significantly increased Lyngbya sp. growth, while additions of N, P and chelated Fe combined (+All) resulted in significantly lower concentrations of microcolin A than in the control. Overall, there was a negative correlation between growth and total concentrations of microcolins A and B. When crude extracts from the control, +FeEDTA and +All treatments of the Lyngbya sp. bioassay were offered to S. striatus in artificial food, they consumed greater quantities of the control and +FeEDTA treatments than the +All. These results provide the first evidence that changes in nutrient availability can affect secondary metabolite concentrations in marine Lyngbya spp. and support previous studies that show that Fe can stimulate growth in benthic marine cyanobacteria. This study also demonstrates quantifiable changes in feeding behavior by a specialist grazer in response to changes in the nutrient conditions under which Lyngbya sp. grows and underscores the need to consider secondary metabolite concentrations, and their effect on grazers, when managing harmful algal blooms.
Uploads
Papers by Judith O'Neil