scholarly journals The 2011 marine heat wave in Cockburn Sound, southwest Australia

Ocean Science ◽  
2012 ◽  
Vol 8 (4) ◽  
pp. 545-550 ◽  
Author(s):  
T. H. Rose ◽  
D. A. Smale ◽  
G. Botting
Keyword(s):  
Dissolved Oxygen ◽  
Heat Wave ◽  
Extreme Events ◽  
Algal Blooms ◽  
Seawater Temperature ◽  
Short Term ◽  
Oxygen Levels ◽  
Australian Coastline ◽  
Western Australian ◽  
Marine Heat Wave

Abstract. Over 2000 km of Western Australian coastline experienced a significant marine heat wave in February and March 2011. Seawater temperature anomalies of +2–4 °C were recorded at a number of locations, and satellite-derived SSTs (sea surface temperatures) were the highest on record. Here, we present seawater temperatures from southwestern Australia and describe, in detail, the marine climatology of Cockburn Sound, a large, multiple-use coastal embayment. We compared temperature and dissolved oxygen levels in 2011 with data from routine monitoring conducted from 2002–2010. A significant warming event, 2–4 °C in magnitude, persisted for > 8 weeks, and seawater temperatures at 10 to 20 m depth were significantly higher than those recorded in the previous 9 yr. Dissolved oxygen levels were depressed at most monitoring sites, being ~ 2 mg l−1 lower than usual in early March 2011. Ecological responses to short-term extreme events are poorly understood, but evidence from elsewhere along the Western Australian coastline suggests that the heat wave was associated with high rates of coral bleaching; fish, invertebrate and macroalgae mortalities; and algal blooms. However, there is a paucity of historical information on ecologically-sensitive habitats and taxa in Cockburn Sound, so that formal examinations of biological responses to the heat wave were not possible. The 2011 heat wave provided insights into conditions that may become more prevalent in Cockburn Sound, and elsewhere, if the intensity and frequency of short-term extreme events increases as predicted.

scholarly journals The 2011 marine heat wave off southwest Australia

2012 ◽  
Vol 9 (2) ◽  
pp. 1691-1703 ◽  
Author(s):  
T. H. Rose ◽  
D. A. Smale ◽  
G. Botting
Keyword(s):  
Dissolved Oxygen ◽  
Heat Wave ◽  
Extreme Events ◽  
Algal Blooms ◽  
Multiple Use ◽  
Short Term ◽  
Oxygen Levels ◽  
Australian Coastline ◽  
Western Australian ◽  
Marine Heat Wave

Abstract. Over 2000 km of Western Australian coastline experienced a significant marine heat wave in February and March 2011. Seawater temperature anomalies of +2–4 °C were recorded at a number of locations and satellite-derived SSTs were the highest on record. Here, we present seawater temperatures from southwestern Australia and describe, in detail, the marine climatology of Cockburn Sound; a large, multiple-use coastal embayment. We compared temperature and dissolved oxygen levels in 2011 with data from routine monitoring conducted from 2002–2010. A significant warming event, 2–4 °C in magnitude, persisted for >8 weeks, and seawater temperatures at 10 to 20 m depth were significantly higher than those recorded in the previous 9 yr. Dissolved oxygen levels were depressed at most monitoring sites, being ~2 mg l−1 lower than usual in early March 2011. Ecological responses to short-term extreme events are poorly understood, but evidence from elsewhere along the Western Australian coastline suggests that the heat wave was associated with high rates of coral bleaching, fish, invertebrate and macroalgae mortalities, and algal blooms. However, more ecological information from Cockburn Sound and other multiple-use embayments is urgently needed. The 2011 heat wave provided insights into conditions that may become more prevalent in Cockburn Sound, and elsewhere, if the intensity and frequency of short-term extreme events increases as predicted.

scholarly journals Effects of multiple disturbances in seagrass meadows: shading decreases resilience to grazing

2009 ◽  
Vol 60 (12) ◽  
pp. 1317 ◽  
Author(s):  
Johan S. Eklöf ◽  
Kathryn McMahon ◽  
Paul S. Lavery
Keyword(s):  
Algal Blooms ◽  
Phytoplankton Blooms ◽  
Short Term ◽  
Field Surveys ◽  
Multiple Disturbances ◽  
Seagrass Meadows ◽  
Management Actions ◽  
Halophila Ovalis ◽  
Black Swans ◽  
Western Australian

Ecosystem shifts are often associated with multiple disturbances, but limited knowledge on the mechanisms involved hampers management. This study investigated how short-term shading affected the resilience of the seagrass Halophila ovalis to grazing by black swans (Cygnus atratus) – a historically dominant grazer currently recovering from hunting and habitat loss – in south-western Australian estuaries, using field surveys and a grazing-shading experiment. Black swans were heterogeneously distributed and, in a high-density site, consumed 23% of seagrass production. Seagrasses recovered rapidly from a single disturbance (i.e. short-term shading or grazing), even though shading alone halved carbohydrate content. When seagrasses were exposed to both disturbances, recovery depended on the type of grazing; where grazing was confined to leaves, leaf densities recovered within 3 weeks, but where grazing was on both leaves and rhizomes there was no recovery. Shading increased the frequency of apex initiation, as did rhizome grazing, but only if the plants had not been shaded. This indicates that shading alters the flow of energy needed to produce apices and leaves following disturbance on rhizomes. Based on the historical swan densities and continuing recurring phytoplankton blooms, management actions reintroducing swans without controlling algal blooms could have an on impact seagrass resilience and associated organisms.

A Survey for Salinity Intrusion and Pollution Assessment in Maputo Estuary

1987 ◽  
Vol 19 (5-6) ◽  
pp. 823-832 ◽  
Author(s):  
J. M. Salomão
Keyword(s):  
Dissolved Oxygen ◽  
Industrial Wastewater ◽  
Pollution Assessment ◽  
Saturation Level ◽  
Salinity Intrusion ◽  
Pollutant Load ◽  
Oxygen Levels ◽  
Salinity Gradients

Following surveys recently carried out in Maputo estuary, a survey with the purpose of acquiring data required to characterize the estuary was carried out in December 1983. After reviewing the hydrology of the tributaries to the estuary, the parameters to be monitored - salinity, conductivity, temperature, and dissolved oxygen, are referred. Finally, taking also into account previous information available, an evaluation of the results, and an assessment of the estuary are done. The estuary can be classified as well mixed, since the vertical salinity gradients found are small. The Umbeluzi estuary, however, is partially mixed. Temperature decreases with the depth, and when moving downstream. Some pollution was found along the lower part of the estuary, probably due to the discharge of domestic and industrial wastewater, which brings the dissolved oxygen figures below the saturation level. As for the upper part of the estuary, the dissolved oxygen levels are not only dependent on the pollutant load, but also on the growing of algae, which by photosynthesis under daylight produce oxygen that dissolves into the water. Quite often, the dissolved oxygen figures are above the saturation level. The growth of algae could be due to the input of phosphorus and nitrogen brought in by the tributary streams. A pollutant load discharged upstream could be the reason for some pollution seen in the Umbeluzi estuary.

scholarly journals The Dynamic Response of Nitrogen Transformation to the Dissolved Oxygen Variations in the Simulated Biofilm Reactor

2021 ◽  
Vol 18 (7) ◽  
pp. 3633
Author(s):  
Qianqian Lu ◽  
Nannan Zhang ◽  
Chen Chen ◽  
Miao Zhang ◽  
Dehua Zhao ◽  
...  
Keyword(s):  
Dissolved Oxygen ◽  
Copy Number ◽  
Stable State ◽  
Quantitative Relationship ◽  
Nitrogen Transformation ◽  
Biofilm Reactor ◽  
Short Term ◽  
Nirs Gene ◽  
Biofilm Reactors ◽  
Recovery Times

Lab-scale simulated biofilm reactors, including aerated reactors disturbed by short-term aeration interruption (AE-D) and non-aerated reactors disturbed by short-term aeration (AN-D), were established to study the stable-state (SS) formation and recovery after disturbance for nitrogen transformation in terms of dissolved oxygen (DO), removal efficiency (RE) of NH4+-N and NO3−-N and activity of key nitrogen-cycle functional genes amoA and nirS (RNA level abundance, per ball). SS formation and recovery of DO were completed in 0.56–7.75 h after transition between aeration (Ae) and aeration stop (As). In terms of pollutant REs, new temporary SS formation required 30.7–52.3 h after Ae and As interruptions, and seven-day Ae/As interruptions required 5.0% to 115.5% longer recovery times compared to one-day interruptions in AE-D and AN-D systems. According to amoA activity, 60.8 h were required in AE-D systems to establish new temporary SS after As interruptions, and RNA amoA copies (copy number/microliter) decreased 88.5%, while 287.2 h were required in AN-D systems, and RNA amoA copies (copy number/microliter) increased 36.4 times. For nirS activity, 75.2–85.8 h were required to establish new SSs after Ae and As interruptions. The results suggested that new temporary SS formation and recovery in terms of DO, pollutant REs and amoA and nirS gene activities could be modelled by logistic functions. It is concluded that temporary SS formation and recovery after Ae and As interruptions occurred at asynchronous rates in terms of DO, pollutant REs and amoA and nirS gene activities. Because of DO fluctuations, the quantitative relationship between gene activity and pollutant RE remains a challenge.

A hybrid model for short-term dissolved oxygen content prediction

2021 ◽  
Vol 186 ◽  
pp. 106216
Author(s):  
Jiande Huang ◽  
Shuangyin Liu ◽  
Shahbaz Gul Hassan ◽  
Longqin Xu ◽  
Cifeng Huang
Keyword(s):  
Dissolved Oxygen ◽  
Oxygen Content ◽  
Hybrid Model ◽  
Short Term

A study of water quality in an urban river and potential improvement using a prototype instream aerator

1989 ◽  
Vol 16 (3) ◽  
pp. 308-316 ◽  
Author(s):  
C. A. Town ◽  
D. S. Mavinic ◽  
B. Moore
Keyword(s):  
Water Quality ◽  
Dissolved Oxygen ◽  
Data Base ◽  
Chlorophyll A ◽  
Late Summer ◽  
Urban River ◽  
Agricultural Activity ◽  
Fish Kills ◽  
Low Dissolved Oxygen ◽  
Oxygen Levels

Urban encroachment and intensive agricultural activity within the Serpentine–Nicomekl watershed (near Vancouver, B.C.) have caused a series of fish (salmon) kills on the Serpentine River since 1980. Low dissolved oxygen was responsible for these kills. This field project investigated some of the dynamic chemical and biological relationships within the river, as well as the use of an instream aerator as a temporary, in situ, water quality improvement measure. Weekly sampling for a 6-month period during the latter half of 1985 established a solid data base for deriving and interpreting meaningful interrelationships. A strong correlation between chlorophyll a and dissolved oxygen levels before the algae die-off supported the hypothesis that algae blooms dying in the fall could create a serious oxygen demand. Because of these environmental conditions, the river is unable to sustain healthy dissolved oxygen levels during this period. As such, a prototype, 460 m artificial aeration line was designed, installed, and monitored to evaluate its potential for alleviating low dissolved oxygen conditions and improving overall water quality during the critical fall period.The instream aerator ran continuously for over 2 months, starting in September 1985. Despite better-than-expected weather conditions (i.e., cool, wet weather) and relatively high dissolved oxygen levels during the fall of 1985, the data base appeared to support the use of this prototype aeration unit as a means of "upgrading" a stretch of an urban river subject to periodic, low dissolved oxygen levels. As a result, a 2-year follow-up study and river monitoring was initiated. In both 1986 and 1987, late summer and early fall river conditions resulted in the potential for serious salmon kills, due to higher-than-normal river temperatures and very low dissolved oxygen. In both instances, the instream aerator prevented such fish kills in a key stretch of the river. Expansion of the system to include other critical stretches of the Serpentine and other urban river systems, near Vancouver, is being considered. Key words: algae, aerator, chlorophyll a, eutrophic, fish kills, instream aeration, river improvement, urban river.

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