Dependance of phytoplankton chlorophyll on bottom resuspension in Cleveland Bay, northern Queensland

1981 ◽  
Vol 32 (6) ◽  
pp. 981 ◽  
Author(s):  
TA Walker
Keyword(s):  
Great Barrier Reef ◽  
Bottom Sediment ◽  
Chlorophyll A ◽  
Water Depth ◽  
Inverse Correlation ◽  
Barrier Reef ◽  
Secchi Disc ◽  
Secchi Disc Depth ◽  
The Mean ◽  
Strong Inverse Correlation

In relatively shallow regions of the lagoon of the central Great Barrier Reef. phytoplankton chlorophyll a concentrations are dependent on intermittent resuspension of bottom sediment by wind-generated waves. This results in a strong inverse correlation between chlorophyll a levels and transparency over a period of time. Bottom resuspension and resettling cause a mide transparency range to occur at any given station. but the mean Secchi disc depth increases linearly with water depth across the lagoon.

Turbidity in the northern Great Barrier Reef lagoon in the wet season, March 1989

1994 ◽  
Vol 45 (4) ◽  
pp. 585 ◽  
Author(s):  
LJ Hamilton
Keyword(s):  
Great Barrier Reef ◽  
Attenuation Coefficient ◽  
Quantitative Relation ◽  
Barrier Reef ◽  
Wet Season ◽  
Secchi Disc ◽  
Reef Lagoon ◽  
Secchi Disc Depth ◽  
Beam Attenuation ◽  
Beam Attenuation Coefficient

In 1989, a typical wet season was experienced in northern Queensland, with low winds and long calm periods. Turbidity in upper waters of the Great Barrier Reef lagoon broadly had a simple distribution that could be modelled from bottom depth contour values alone, without introducing wind speed or bottom type. In the absence of major storm and cyclone events, this result appears to be general, based on the similarity between March 1989 survey data and Secchi disc climatology. The simple distribution arises because the main turbidity sources are riverine discharges, with little entrainment of bottom sediment into the upper column, except in shallower waters. Fresh, highly turbid riverine influxes are generally confined close inshore, with salinity and Secchi contours parallel to shore, forming cross-shelf gradients. A semi-quantitative relation was found between sea surface colour and Secchi disc depth. Examination of nephelometric turbidity stratification showed that satellite and Secchi data should be more useful for subsurface turbidity inference between Cooktown and Innisfail than in Princess Charlotte Bay, with horizontal and vertical stratifications, respectively, observed in those areas. Highest nephelometric turbidity was seen from Cooktown to Innisfail. Beam attenuation coefficient in oceanic waters outside the reef appeared to be dominated by absorption, with lagoon waters influenced by scattering. A method is suggested to enable approximate transfer of beam attenuation coefficient measured by a transmissometer operating at a single wavelength to beam attenuation coefficient at other wavelengths, using coincident measurements of Secchi disc depths made with filters.

scholarly journals Grania (Annelida: Clitellata: Enchytraeidae) of the Great Barrier Reef, Australia, including four new species and a re-description of Grania trichaeta Jamieson, 1977

Zootaxa ◽  
2009 ◽  
Vol 2165 (1) ◽  
pp. 16-38 ◽  
Author(s):  
PIERRE DE WIT ◽  
EMILIA ROTA ◽  
CHRISTER ERSÉUS
Keyword(s):  
New Species ◽  
Great Barrier Reef ◽  
New Caledonia ◽  
Barrier Reef ◽  
Interspecific Divergence ◽  
Eastern Australia ◽  
New Material ◽  
Voucher Specimens ◽  
The Mean ◽  
Phylogenetic Affinities

This study describes the fauna of the marine enchytraeid genus Grania at two locations on the Australian Great Barrier Reef: Lizard and Heron Islands. Collections were made from 1979 to 2006, yielding four new species: Grania breviductus sp. n., Grania regina sp. n., Grania homochaeta sp. n. and Grania colorata sp. n.. A re-description of Grania trichaeta Jamieson, 1977 based on new material is also included, along with notes and amendments on G. hyperoadenia Coates, 1990 and G. integra Coates & Stacey, 1997, the two latter being recorded for the first time from eastern Australia. COI barcode sequences were obtained from G. trichaeta and G. colorata and deposited with information on voucher specimens in the Barcode of Life database and GenBank; the mean intraspecific variation is 1.66 % in both species, while the mean interspecific divergence is 25.54 %. There seem to be two phylogeographic elements represented in the Great Barrier Grania fauna; one tropical with phylogenetic affinities to species found in New Caledonia and Hong Kong, and one southern (manifested at the more southerly located Heron Island) with affinities to species found in Southern Australia, Tasmania and Antarctica.

Spatial and temporal patterns of near-surface chlorophyll a in the Great Barrier Reef lagoon

2007 ◽  
Vol 58 (4) ◽  
pp. 342 ◽  
Author(s):  
J. Brodie ◽  
G. De'ath ◽  
M. Devlin ◽  
M. Furnas ◽  
M. Wright
Keyword(s):  
Great Barrier Reef ◽  
Chlorophyll A ◽  
Agricultural Development ◽  
Monitoring Program ◽  
Barrier Reef ◽  
Spatial And Temporal Patterns ◽  
Wet Season ◽  
Near Surface ◽  
Nutrient Delivery ◽  
Inshore Waters

Surface chlorophyll a concentrations in the Great Barrier Reef (GBR) lagoon were monitored at individual stations for periods of 6 to 12 years. The monitoring program was established to detect spatial and temporal changes in water quality resulting from increased loads of nutrients exported from the catchments adjoining the GBR. Sampling occurred monthly at up to 86 sites that were located in transects across the width of the continental shelf. In the central and southern GBR (16–21°S), there was a persistent cross-shelf chlorophyll a gradient, with higher concentrations near the coast. No cross-shelf gradient was observed in the far northern GBR (12–15°S). Mean chlorophyll a concentrations in the far northern GBR (0.23 µg L–1) were less than half those in the south and central GBR (0.54 µg L–1). Chlorophyll a varied seasonally within regions, with mean summer-wet season (December–April) concentrations ~50% greater than those in the winter-dry season (May–November). Sub-annual, inter-annual and event-related variations in chlorophyll a concentrations were observed in several zones. Multi-year patterns in concentrations suggest that relatively short (5–8 years) time series may give spurious estimates of secular trends. Higher chlorophyll a concentrations in inshore waters south of 16°S were most likely related to the levels of river nutrient delivery associated with agricultural development on adjacent catchments.

scholarly journals Effect of Phosphorous Loadings on Macrophytes Structure and Trophic State of Dam Reservoir on a Small Lowland River (Eastern Poland)

2013 ◽  
Vol 39 (3) ◽  
pp. 33-46 ◽  
Author(s):  
Monika Tarkowska-Kukuryk
Keyword(s):  
Chlorophyll A ◽  
Trophic State ◽  
Water Current ◽  
Trophic State Index ◽  
Lowland River ◽  
Dam Reservoir ◽  
Secchi Disc ◽  
Eutrophic Lakes ◽  
Secchi Disc Depth ◽  
Dam Site

Abstract The main objective of the study was to evaluate if macrophytes structure and trophic status of dam reservoir Kraśnik on a small lowland river Wyżnica are determined by phosphorous loadings. Studies were conducted seasonally in May, July and October during the years 2008-2009. Samples were taken at four sites: Site 1 - inflow of the Wyżnica River to pre-dam, Site 2 − pre-dam, Site 3 − dam reservoir and Site 4 - outflow of the Wyżnica River from dam reservoir. Physical and chemical parameters (temperature, Secchi disc depth, dissolved oxygen, pH, conductivity, total suspension, chlorophyll-a, TP and P-PO4) were measured in water samples. Together with water parameters there were estimated biomass of phytoplankton and species composition and biomass of emergent, floating-leaved and submerged macrophytes. Concentrations of TP, chlorophyll-a and Secchi disc depth were used to calculate trophic state index of Carlsson for dam reservoir and its pre-dam. Based on mean water current, mean residence time of water in dam reservoir and concentrations of TP and P-PO4 loadings (g m-2) flowing into dam reservoir with the Wyżnica River were calculated. The results showed visible negative effect of phosphorous loadings on both macrophytes composition and trophic state of the reservoir. The marked changes concerned soft vegetation. High P loadings (7.74 g m-2 of TP and 6.03 g m-2 P-PO4) during the spring of 2008 caused the disappearance of characeans meadows. In 2009, the presence of rigid hornwort (Ceratophyllum demersum L.), the species typical for eutrophic lakes was noted. This unrooted submerged plant uptakes dissolved orthophosphates directly from the water column. Values of Carlsson index (51.4 ≤ TSI ≤ 68.2) indicate the eutrophic state of dam reservoir Kraśnik. During summer season in dam reservoir there were observed algal blooms (biomass of phytoplankton exceed 10 mg WW dm-3) and low water transparency (Secchi disc depth ranged from 0.4 to 0.65 m). During the two-year studies in dam reservoir Kraśnik a high reduction of P loadings, mostly dissolved orthophosphates was observed. Dependently on season, reduction of P-PO4 loadings ranged from 52% (July 2008) up to 91% (May 2009). The reduction of TP was lower and reached values from 15% (May 2008) to 48% (July 2009).

Demographic variability and long-term change in a coral reef sponge along a cross-shelf gradient of the Great Barrier Reef

2010 ◽  
Vol 61 (4) ◽  
pp. 389 ◽  
Author(s):  
R. J. Bannister ◽  
C. N. Battershill ◽  
R. de Nys
Keyword(s):  
Coral Reefs ◽  
Continental Shelf ◽  
Great Barrier Reef ◽  
Anthropogenic Impacts ◽  
Barrier Reef ◽  
Outer Reef ◽  
Reef System ◽  
Anthropogenic Inputs ◽  
Term Change ◽  
The Mean

Effects of anthropogenic inputs on corals are well documented in regard to the ecology of coral reefs. However, responses to anthropogenic changes by sponge assemblages, also a key component of coral reefs, have received less attention. This paper quantifies differences in abundance, size and distribution of the sponge Rhopaloeides odorabile across a cross-shelf reef system on the central Great Barrier Reef (GBR) from neritic to outer reef oligotrophic waters. Benthic surveys were conducted in reef habitats spatially separated across the continental shelf. The mean abundance of R. odorabile increased significantly with increasing distance from coastal habitats, with 3.5 times more individuals offshore than inshore. In contrast, the mean size (volume) of R. odorabile individuals did not differ significantly across the cross-shelf reef system. On inshore reefs, R. odorabile was restricted to depths <10 m, with a preference for shallower depths (5–6 m). On offshore reefs, R. odorabile was found as deep as 15 m and predominantly between 9 and 10 m. These demographic changes in R. odorabile populations, together with a general population size reduction from surveys made decades prior, suggest a response to anthropogenic impacts across the continental shelf of the central GBR.

scholarly journals Physico-chemical aspects of Chandbill Oxbow lake of Meherpur, Bangladesh

1970 ◽  
Vol 20 (1) ◽  
pp. 31-39
Author(s):  
AKM Nazrul Kabir ◽  
M Niamul Naser
Keyword(s):  
Dissolved Oxygen ◽  
Water Depth ◽  
Secchi Depth ◽  
Ammonia Nitrogen ◽  
Total Alkalinity ◽  
Oxbow Lake ◽  
Total Hardness ◽  
Secchi Disc ◽  
Secchi Disc Depth ◽  
Physico Chemical

Some physico-chemical parameters of Chandbill Baor, a natural oxbow lake of Meherpur district were studied from September 2006 to August 2007. Air temperature of the study area varied from 18.10 to 32.10°C (x-bar± SE : 27.73 ± 1.22°C). The Water temperature (17.10 to 32.10°C; x-bar± SE: 28.24 ± 1.32°C), Secchi disc depth (8.89 to 53.34 cm; x-bar± SE : 26.19 ± 4.29 cm), water depth (132.08 to 307.34 cm; x-bar± SE : 183.93 ± 13.88 cm); total alkalinity (51.3 to 85.5 mg/l; x-bar± SE : 68.4 ± 3.64 mg/l), total hardness (85.5 to 188.10 mg/l; x-bar± SE : 125.81 ± 9.38 mg/l), dissolved oxygen (5.0 to 12.0 mg/l; x-bar± SE: 8.42 ± 0.62 mg/l), free CO2 (5.0 to 30.0 mg/l; x-bar± SE : 14.58 ± 2.64 mg/l), pH (8.0 to 10; x-bar± SE : 8.54 ± 0.19), ammonia-nitrogen (0.3 to 0.7 mg/l; x-bar± SE: 0.46 ± 0.04 mg/l) in the 'Baor' water were found to be suitable for survival of aquatic fauna. Nitrite-nitrogen was absent in the 'em>Baor' throughout the year. Positive correlations were observed in between air and water temperature (r = 0.978); free CO2 and Secchi depth (r = 0.839), free CO2 and water depth (r = 0.714); water depth and Secchi depth (r = 0.903); total hardness and total alkalinity (r = 0.861) and pH with DO (r = 0.661). However, inverse relations were observed among ammonia-nitrogen with water depth (r = −0.727); ammonia-nitrogen with Secchi disc depth (r = −0.840); dissolved oxygen with free CO2 (r = −0.636); pH with Secchi disc depth (r = −0.581) and pH with free CO2 (r = −0.825). The productivity of the lake was found to be medium and could be improved to higher level. Alkaline pH (8.54 ± 0.19) was supposed to be helpful for proper growth and development of fishes and aquatic organisms. This is the first limnological report from a natural ‘Baor’ (Oxbow lake) of Meherpur district, Bangladesh.Key words: Physico-chemical aspects; Oxbow lake; MeherpurDOI: http://dx.doi.org/10.3329/dujbs.v20i1.8835Dhaka Univ. J. Biol. Sci. 20(1): 31-39, 2011 (January)

scholarly journals Increases in Picocyanobacteria Abundance in Agriculturally Eutrophic Pampean Lakes Inferred from Historical Records of Secchi Depth and Chlorophyll-a

Water ◽  
2022 ◽  
Vol 14 (2) ◽  
pp. 159
Author(s):  
Horacio Ernesto Zagarese ◽  
Nadia R. Diovisalvi ◽  
María de los Ángeles González Sagrario ◽  
Irina Izaguirre ◽  
Paulina Fermani ◽  
...  
Keyword(s):  
Chlorophyll A ◽  
Size Structure ◽  
Generalized Additive Models ◽  
Secchi Depth ◽  
Additive Models ◽  
Validation Dataset ◽  
Secchi Disc ◽  
Secchi Disc Depth ◽  
Before And After ◽  
Pampa Region

Phytoplankton size structure has profound consequences on food-web organization and energy transfer. Presently, picocyanobacteria (size < 2 µm) represent a major fraction of the autotrophic plankton of Pampean lakes. Glyphosate is known to stimulate the development of picocyanobacteria capable of degrading the herbicide. Due to the worldwide adoption of glyphosate-resistant crops, herbicide usage has increased sharply since the mid-1990s. Unfortunately, there are very few studies (none for the Pampa region) reporting picocyanobacteria abundance before 2000. The proliferation of µm sized particles should decrease Secchi disc depth (ZSD). Therefore ZSD, conditional to chlorophyll-a, may serve as an indicator of picocyanobacteria abundance. We use generalized additive models (GAMs) to analyze a “validation” dataset consisting of 82 records of ZSD, chlorophyll-a, and picocyanobacteria abundance from two Pampean lakes surveys (2009 and 2015). In support of the hypothesis, ZSD was negatively related to picocyanobacteria after accounting for the effect of chlorophyll-a. We then fitted a “historical” dataset using hierarchical GAMs to compare ZSD conditional to chlorophyll-a, before and after 2000. We estimated that ZSD levels during 2000–2021 were, on average, only about half as deep as those during 1980–1999. We conclude that the adoption of glyphosate-resistant crops has stimulated outbreaks of picocyanobacteria populations, resulting in lower water transparency.

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