Growth of Halodule wrightii in culture and the effects of cropping, light, salinity and atrazine

Mitchell, Christine A.

doi:10.1016/0304-3770(87)90054-4

Cited by 11 publications

(8 citation statements)

References 40 publications

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“…Several studies of terrestrial plant systems have found that moderate levels of grazing can stimulate above-ground productivity by increasing shoot growth rates and the number of shoots produced (Belsky 1986). Cropping experiments on the seagrass Halodule wrightii by Mitchell (1987) demonstrated that trimming the ramets stimulated the production of new ramets, and that the most severely cropped plants had the greatest increase in ramet numbers. Like Halodule wrightii, Z. novazelandica grows by basal elongation of the meristemic region (Kuo & McComb 1989), and ramets react to cropping by producing new ramets (Mitchell 1987).…”

Section: Discussionmentioning

confidence: 99%

“…Cropping experiments on the seagrass Halodule wrightii by Mitchell (1987) demonstrated that trimming the ramets stimulated the production of new ramets, and that the most severely cropped plants had the greatest increase in ramet numbers. Like Halodule wrightii, Z. novazelandica grows by basal elongation of the meristemic region (Kuo & McComb 1989), and ramets react to cropping by producing new ramets (Mitchell 1987). Grazing of Thalassia testudinum by sea urchins has been shown to have no negative effect on seagrass biomass due to a compensatory increase in the number of short shoots during the growing season (Valentine et al 1997).…”

Section: Discussionmentioning

confidence: 99%

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Patch dynamics and response to disturbance of the seagrass Zostera novazelandica on intertidal platforms in southern New Zealand

Ramage¹,

Schiel²

1999

Mar. Ecol. Prog. Ser.

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We examined the patch dynamics of the intertidal seagrass Zostera novazelandica on 2 reef platforms in order to understand the processes governing the establishment, maintenance and mortality of patches. The size distribution of patches at 3 tidal heights (low, mid and high shore) was assessed. Eighty patches, ranglng in initial size from 0.1 to 2.4 m2 surface area, were tagged and video image analysis was used bi-monthly for 14 mo to calculate rates of expansion and contraction of these patches. Permanently marked 150 m2 areas of reef were monitored monthly to record patch recruitment and mortality. Initially, 75% of patches were <0.5 m2 All patches decreased in size during winter, probably due to increased wave action, and expanded during spring and summer. The proportional expansion and contraction of patches was independent of initial patch size. At the end of the study the size distribution of patches was similar to the initial distribution. Patch mortality was restricted to those <0.4 m2, of which 60% disappeared during the study. Larger patches suffered partial mortality through fragmentation. No large patches were formed through the amalgamation of smaller patches. Seedlings recruited into small sediment pockets in tidepools during spring, but few survived through summer because of removal by wave action. Experimental perturbation of patches resulted in increased erosion followed by decreased growth rates and, in many small patches, mortality. Removing only seagrass blades, however, resulted in increased production of new shoots relative to controls. Overall, seagrass patches are susceptible to disturbance, successful rclcruitment by seedlings may be rare or at least episodic, and populations are probably long-Lived and depend on slow vegetative growth for maintenance and expansion.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Patch dynamics and response to disturbance of the seagrass Zostera novazelandica on intertidal platforms in southern New Zealand

Ramage¹,

Schiel²

1999

Mar. Ecol. Prog. Ser.

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“…Chemicals such as atrazine and pentachlorophenol (at concentrations of 1 ppm) depressed the rate of oxygen evolution (photosynthesis) and oxygen uptake (respiration) of leaves of T. testudinum [143]. Atrazine (30 ppm) caused a significant reduction in survival, production of new ramets, above‐sediment biomass (greater than 50%), and growth of H. wrightii [144]. Cropping and variation in light and salinity did not influence the biological response to atrazine.…”

Section: Status Of Knowledge About Chemical Stressors In Tropical Marmentioning

confidence: 99%

Ecotoxicology of tropical marine ecosystems

Peters

Gassman

Firman

et al. 1997

Enviro Toxic and Chemistry

315

133

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Abstract-The negative effects of chemical contaminants on tropical marine ecosystems are of increasing concern as human populations expand adjacent to these communities. Watershed streams and ground water carry a variety of chemicals from agricultural, industrial, and domestic activities, while winds and currents transport pollutants from atmospheric and oceanic sources to these coastal ecosystems. The implications of the limited information available on impacts of chemical stressors on mangrove forests, seagrass meadows, and coral reefs are discussed in the context of ecosystem management and ecological risk assessment. Three classes of pollutants have received attention: heavy metals, petroleum, and synthetic organics such as herbicides and pesticides. Heavy metals have been detected in all three ecosystems, causing physiological stress, reduced reproductive success, and outright mortality in associated invertebrates and fishes. Oil spills have been responsible for the destruction of entire coastal shallow-water communities, with recovery requiring years. Herbicides are particularly detrimental to mangroves and seagrasses and adversely affect the animal-algal symbioses in corals. Pesticides interfere with chemical cues responsible for key biological processes, including reproduction and recruitment of a variety of organisms. Information is lacking with regard to long-term recovery, indicator species, and biomarkers for tropical communities. Critical areas that are beginning to be addressed include the development of appropriate benchmarks for risk assessment, baseline monitoring criteria, and effective management strategies to protect tropical marine ecosystems in the face of mounting anthropogenic disturbance.

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“…Salinity tolerance of seagrass species. Source is indicated: (1) Den Hartog (1970), (2) Jagtap (1991), (3) Poiner et al (1987), (4) Mitchell (1987), (5) Hillman et al (1995), (6) Brouns & Heijs (1985), (7) Aioi & Pollard (1993), (8) Erftemeijer & Herman (1994), (9) Kohout & Kolipinski (1967) …”

Section: Discussionmentioning

confidence: 99%

Groundwater effects on diversity and abundance of lagoonal seagrasses in Kenya and on Zanzibar Island (East Africa)

Kamermans¹,

Hemminga²,

Tack³

et al. 2002

Mar. Ecol. Prog. Ser.

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Seagrass species diversity and abundance were studied in East African back-reef lagoons with contrasting groundwater-outflow rates. The selection of the lagoons was based on a groundwater flow model. A total of 10 seagrass species was observed at all sites together. Sites with a higher groundwater outflow displayed a lower species diversity than sites with a lower groundwater outflow. Thalassodendron ciliatum dominated at sites with high groundwater outflow rates, while Thalassia hemprichii showed higher coverage at sites with low groundwater outflow. Porewater salinities were up to 5 psu lower at locations with predicted high groundwater-outflow rates indicating supply of freshwater. The reduction in porewater salinity at groundwater outflow sites is relatively low, which makes it unlikely that a difference in optimum salinity for growth is the main factor causing reduced diversity at these sites. Nitrogen-stable isotope signatures of seagrass leaves showed a significant increase with increased groundwater outflow rates. This suggests that the nitrogen source for these plants was, at least in part, groundwater. Differences in competition for nitrogen may explain the observed pattern in species diversity and abundance. To establish a substantive link between the observed reduced seagrass diversity or enhanced δ 15 N values of T. ciliatum leaves on the one hand and increased groundwater outflow rates on the other, further exploration through detailed measurements of groundwater outflow rates and groundwater nitrogen isotopic composition are needed.

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Growth of Halodule wrightii in culture and the effects of cropping, light, salinity and atrazine

Cited by 11 publications

References 40 publications

Patch dynamics and response to disturbance of the seagrass Zostera novazelandica on intertidal platforms in southern New Zealand

Patch dynamics and response to disturbance of the seagrass Zostera novazelandica on intertidal platforms in southern New Zealand

Ecotoxicology of tropical marine ecosystems

Groundwater effects on diversity and abundance of lagoonal seagrasses in Kenya and on Zanzibar Island (East Africa)

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