Understanding Blue Green Algae Blooms in Myall Lakes NSW

194 Pages·2004·2.22 MB·English

Understanding Blue Green Algae
Blooms in Myall Lakes NSW.
NSW Department of Infrastructure, Planning and Natural Resources
As of the 2nd April 2003 the Department of Land and Water Conservation (DLWC) was
abolished by the NSW State Parliament and the Department of Sustainable Natural Resources
(DSNR) established. As of the 29th May 2003 the Department of Sustainable Natural Resources
was abolished and replaced by the Department of Infrastructure, Planning and Natural
Resource (DIPNR). Hence most references to DLWC have been changed to DIPNR. However as
many aspects of this project, including contracts between DLWC and Environment Australia,
were undertaken prior to the 2nd April, reference is still made to DLWC in this document where
appropriate.
NSW Department of Infrastructure, Planning and Natural Resources
Understanding Blue Green Algae
Blooms in Myall Lakes NSW.
Prepared by:
Matthew Dasey, Joanne Wilson, Natasha
Ryan, Graham Carter, Nick Cook, Susana
Realica-Turner and
Edited By:
Matthew Dasey, Allan Raine,
Natasha Ryan, Joanne Wilson and Nick
Cook
Supported by:

NSW Department of Infrastructure, Planning and Natural Resources
Acknowledgments
This report was prepared with technical contributions from Lee
Bowling (CNR), Peter Scanes (EPA), Anna Redden (University of
Newcastle), Graham Harris (CSIRO) and Monika Muschal
(CNR). Also DIPNR would like to thank the residents of the
Myall Lakes area who greatly assisted in providing information on
the history of the lakes.
Published by:
New South Wales Department of Infrastructure,
Planning and Natural Resources
Hunter Region
July 2004
NSW Government
ISBN 0 7347 5498 1
Cover photographs – Myall Lakes. Taken by Joanne Wilson and Graham Carter
NSW Department of Infrastructure, Planning and Natural Resources
Understanding Blue Green Algae Blooms
in Myall Lakes NSW.
Contents
Page
EXECUTIVE SUMMARY I
1. INTRODUCTION 1
1.1 Background 1
1.2 Scope and Objectives of the Coast and Clean Seas Project 3
1.3 Myall Lakes in Comparison to other Australian coastal lakes and estuaries 4
1.3.1 Classification of Coastal Waterways 4
1.3.2 Classification of the health and status of coastal waterways in Australia 4
1.4 Nutrient dynamics in estuaries and coastal lakes 7
1.4.1 The sources of nutrients 7
1.4.2 Nutrient limitations, cycling and algal production 8
1.4.3 Response of lakes and estuaries to nutrient loads 9
2. CHARACTERISTICS OF MYALL LAKES AND ITS CACTCHMENT 11
2.1 Location of Study Area 11
2.2 Characteristics of the Myall Lakes region 11
2.2.1 Climate 12
2.2.2 Geology and soils 14
2.2.3 Preliminary geomorphic status of the Myall River catchment 15
2.2.4 Settlement History and Landuse 18
2.2.5 Human Settlement 19
2.3 Characteristics of the Myall Lakes System 20
2.3.1 Geography 20
2.3.2 Lake Flushing 20
2.3.3 Lake Structure and Bathometry 21
2.3.4 Sedimentology of the Broadwater, Myall Lakes NSW 23
2.3.5 Benthic Nutrient Fluxes in Bombah Broadwater, Myall Lakes 24
2.3.6 Groundwater quality 26
2.3.6.1 Groundwater Electrical Conductivity 28
2.3.6.2 Groundwater pH 29
2.3.6.3 Groundwater Chemical composition 29
2.3.6.4 Indications of Possible sewage contamination 30
2.3.6.4.1 Faecal Bacteria 30
2.3.6.4.2 Nutrients 30
2.3.6.4.3 Nutrient Trends versus Water Level Trends 32
2.3.6.4.4 Nutrients and Park Occupancy 32
2.3.3.4.5 Synopsis 33
3. NUIRIENT SOURCES TO MYALL LAKES 35
3.1 Catchment nutrient inputs to Myall Lakes 35
3.1.1 Catchment Management Support System Modelling 35
3.1.1.1 Comparison of loads arising in Myall Lake sub-catchments 36
3.1.1.2 CMSS Estimates of historical and contemporary annual nutrient loads 37
3.1.1.3 CMSS Estimates of nutrient source arising from different land uses 38
3.1.2 Estimates if nutrient load from River volume 39
3.1.3 Measured Nutrient Exports from the Catchment - autosampler results 39
3.1.4 Results from Water Quality Monitoring in the Myall River 40
3.1.5 Atmospheric Nutrient Contributions 43
3.1.6 Potential nutrient contributions from National Park visitor sewage waste 43
NSW Department of Infrastructure, Planning, and Natural Resources
Understanding Blue Green Algae Blooms
in Myall Lakes NSW.
3.1.7 Estimated Phosphorus load from Groundwater inflows 43
3.1.8 Estimate of Myall Lakes System nutrient loading per unit lake surface area 44
4. PHYTOPLANKTON ABUNDANCE AND DISTRIBUTION 45
4.1 Background 45
4.1.1 Phytoplankton community as an indicator of estuarine health 45
4.1.1.1 Changes in phytoplankton community and ecological succession 46
4.1.2 Some Characteristics of Blue-Green Algae 48
4.1.2.1 Adaptations of Blue-Green Algae 48
4.1.2.2 Ambient conditions that enhance Blue-Green algal growth 49
4.1.2.3 Human health implications of Blue-Green algae 50
4.2 Methods 51
4.2.1 Aims of the monitoring study 51
4.2.2 Algal sampling and analysis 51
4.2.3 Data Analyses and presentations 52
4.3 Results 53
4.3.1 Spatial Distributions of Blue-Green Algae 53
4.3.2 Blue-Green Algal community change and succession 55
4.3.2.1 Multivariate analysis of temporal and spatial trends in the Blue-Green Algae
Community 55
4.3.2.2 Phase 1 - Blue-Green Algal Bloom 56
4.3.2.3 Phase 2 - Blue-Green Algal Bloom 57
4.3.2.4 Phase 3 - Blue-Green Algal Bloom 58
4.3.3 The response of algal community composition to changing conductivity 59
4.3.4 Descriptions of phytoplanktonic community succession in Myall Lakes 62
4.3.4.1 Upper Myall Rivermouth 63
4.3.4.2 Bombah Braodwater 63
4.3.4.3Two-Mile and Boolambayte Lakes 64
4.3.4.4 Myall Lake 66
4.3.4.5 Some observed patterns of phytoplankton diversity and abundance 67
4.4 Discussion 68
4.4.1 The role of conductivity in algal community composition change 68
4.4.2 Patterns of nutrient concentration and the algal community in Myall Lakes 68
4.4.3 Other factors influencing the composition of Blue-Green Algae communities 70
5. WATER QUALITY 72
5.1 Water Nutrients 72
5.1.1 Introduction 72
5.1.2 Methods 73
5.1.2.1 Rainfall 73
5.1.2.2 Water nutrient analyses 73
5.1.2.3 Near-Benthic Water collection 74
5.1.2.4 Interpreting nutrient data against ANZECC and ARMCANZ guidelines 74
5.1.2.5 Data consolidation and presentation 75
5.1.3 Results 76
5.1.3.1 Rainfall 77
5.1.3.2 Total Phosphorus 78
5.1.3.3 Soluble Reactive Phosphorus 78
5.1.3.4 Total Nitrogen 80
5.1.3.5 Ammonium 81
5.1.3.6 Nitrate/Nitrite 81
5.1.3.7 Chlorophyll a 81
5.1.3.8 Near-Benthic Water Collection 92
NSW Department of Infrastructure, Planning, and Natural Resources
Understanding Blue Green Algae Blooms
in Myall Lakes NSW.
5.1.4 Discussion 93
5.1.4.1 Temporal and spatial patterns of nutrient distribution 93
5.1.4.2 N Near-Benthic Water Collection 95
5.2 Nitrogen Stable Isotope signatures of Aquatic Plants 96
5.2.1 Introduction 96
5.2.2 Methods 97
5.2.3 Results 99
5.2.4 Discussion 100
5.3 Physico-chemical parameters 100
5.3.1 Introduction 100
5.3.2 Methods 101
5.3.3 Results 102
5.3.3.1 Stratification 110
5.3.3.2 Light availability 112
5.3.4 Discussion Physico-chemical water quality 116
6. AQUATIC VEGETATION AND LAKE HABITAT 119
6.1 Background 119
6.1.1 Vegetation 119
6.1.2 Lakebed sediments 120
6.2 Methods
6.2.1 Vegetation assessment method 121
6.2.2 Lakebed assessment method 122
6.3 Results 123
6.3.1 Vegetation 123
6.3.2 Types of aquatic plants found in Myall Lakes 124
6.3.3 Spatial Distribution of plants in Myall Lakes 131
6.3.4 Temporal Change in the Distribution of plants in Myall Lakes 133
6.3.4.1 Najas marina and Charophytes - Annual growth cycles 133
6.3.4.2 Vallisneria gigantea - Broadwater die-off 134
6.3.4.3 Potamogeton perfoliatus - Widespread colonisation 134
6.3.5 Benthic Survey - Results and Discussion 134
6.3.5.1 Percent Total Organic Carbon (TOC) 135
6.3.5.2 Total Nitrogen (TN) 135
6.3.5.3 Total Phosphorus (TP) 135
6.3.5.4 Total Sulphur (TS) 136
6.3.5.5 Grainsize Analysis 136
6.3.5.6 Benthic Microcystis sp 139
6.4 Discussion 140
6.4.1 Vegetation 140
6.4.2 Benthic Nutrient Content 143
6.4.3 General Discussion 143
7. SYNTHESIS OF THE DATA 145
7.1 What are the physical and biological conditions/processes, which contribute to
Blue-Green Algal blooms in Myall Lakes 145
7.2 What are the relative contributions of nutrient sources to algal growth in the lakes? 149
7.2.1 The role of nutrients in algal growth 149
7.2.2 Sources of nutrients to Myall Lakes 149
7.2.2.1 Rainfall 149
7.2.2.2 Groundwater 149
7.2.2.3 Catchment Inflows 150
7.2.2.4 Nutrient recycling within the lakes 150
NSW Department of Infrastructure, Planning, and Natural Resources
Understanding Blue Green Algae Blooms
in Myall Lakes NSW.
7.2.3 Summary of nutrient source data 152
7.3 What is the nutrient status of Myall Lakes 152
7.3.1 Techniques to assess nutrient status 153
7.3.2 Assessing the nutrient status of Myall Lakes 154
7.3.3 Risks due to increasing nutrients 158
7.4 Supporting the development of effective management strategies to reduce
catchment loads 159
7.4.1 Regional Strategic Focus: Lower North Coast Catchment Blueprint 159
7.4.2 Local Catchment Level: Myall Community Catchment Plan 160
7.4.3 Specific Initiatives: Dairy Industry trials to investigate effectiveness of buffer strips 161
7.5 Developing pro-active assessment protocols to assist in the management of future
algal blooms 165
7.6 Myall Lakes - Where to from here? 166
7.6.1 Continued Monitoring in Myall Lakes and its Catchment 166
7.6.2 Additional ongoing investigations 167
7.6.3 Future Studies 168
8. REFERENCES 170
9. APPENDICES 176
NSW Department of Infrastructure, Planning, and Natural Resources
Executive summary Understanding Blue Green Algae Blooms
in Myall Lakes NSW
Executive summary
Myall Lakes is one of the largest coastal lake systems in New South Wales boasting over ten
thousand hectares of waterways set wholly within the Myall Lakes National Park. The Myall
Lakes system comprises a series of lakes including the Bombah Broadwater (lower lake),
Two Mile and Boolambayte Lakes (mid-lakes) and Myall Lake (upper lake). Feeding this lake
system is a catchment area of 78,000 hectares. The Myall and Crawford rivers are the main
tributaries to the lake system, feeding into Bombah Broadwater, while Boolambayte Creek
also supplies fresh water. The Lower Myall River connects this unique waterbody to the
ocean, allowing saltwater exchange from Port Stephens. Myall Lakes has significant
environmental and cultural value to the local, national and international community. The lake
system is recognised internationally under the Ramsar Convention as an important wetland,
and Myall Lakes National Park is a popular tourist destination for camping, bushwalking,
fishing, boating and water sports. A healthy lake system is integral to the culture and
economy of the local area.
In early 1999 Myall Lakes began to exhibit major signs of a natural system in trouble when a
large, toxic blue-green algae bloom formed in the lower section of the lakes. Blue-green algae
are a type of bacteria that act like plants by using light for photosynthesis. When conditions
are ideal they can multiply at a prolific rate resulting in a bloom. Potentially harmful algal
scums accumulated on the shores of the lake including at many popular camping areas. The
bloom persisted on-and-off until April 2001 having a major impact on the local community –
tourist numbers dropped and the lakes were intermittently closed to commercial and
recreational fishing. Blue-green algal blooms have continued to occur in the lakes since mid
2001, although not as severely as those experienced in 1999.
The initial algal bloom in 1999 left the Myall Lakes community extremely concerned about
the future of their unique natural asset. The State Government responded to these concerns by
initiating the ‘Monitoring Blue-Green Algae in Myall Lakes’ project - a partnership between
the then Department of Land and Water Conservation (DLWC; now Department of
Infrastructure, Planning, and Natural Resources [DIPNR]) and the NSW National Parks and
Wildlife Service (NPWS: now part of the Department of Environment and Conservation
[DEC]) with funding from the Federal Government’s Coasts and Clean Seas program. The
project was designed to:
? understand the combination of factors that cause algal blooms in the lakes;
? determine the overall health of the Myall Lakes system; and
NSW Department of Infrastructure, Planning and Natural Resources I
Executive summary Understanding Blue Green Algae Blooms
in Myall Lakes NSW
? predict the likelihood that they would occur again.
This information was considered vital to ensure future resources could be effectively targeted
to manage the lakes system, and the impact of possible future algal blooms.
Information collected during the study (2001–2002) was combined with information collected
prior to 2001, and from recent catchment studies. Interpretation of the many sources of
information was complex, and in many cases, characteristics of both eutrophic and
mesotrophic environments occurred simultaneously or sequentially in the same area.
However, a picture has emerged of the major nutrient sources, temporal and spatial patterns in
physical and ecological characteristics of Myall Lakes, and the likelihood of toxigenic algal
blooms occurring in the future.
The period over which information was available (1999-2002) encompassed both above and
below average rainfall conditions, and extended throughout the entire Myall Lakes region.
During the period of the project (2001-2002), below average rainfall was experienced, and no
toxigenic algal blooms occurred. This study highlighted the naturally high variability in
physical and ecological characteristics among the interconnected lakes and between ‘wet’ and
‘dry’ periods. During the study a benthic organic microalgal layer was discovered over much
of the bed of Myall Lake and some of the mid-lakes region. The role this layer plays in the
ecology of the lake is yet to be determined, though some speculation is made in this report.
The study showed that catchment runoff from the Upper Myall River is currently the most
important source of ‘new’ nutrients contributing to the formation of toxigenic algal blooms in
Myall Lakes (noting that a significant amount of nutrient is already ‘stored’ within the lake
sediments). Due to long flushing times, the lake acts as an effective trap for nutrients, organic
matter and sediments and is therefore highly vulnerable to increased inputs from the
catchment. The naturally low flushing also results in increased importance of the processing
of organic matter and nutrients by processes occurring in the lake sediments.
The status of the three main regions of the lake system is discussed separately below.
Broadwater
The occurrence of toxigenic algal blooms in the Broadwater in 1999 alerted the community
and natural resource managers to the potentially eutrophic status of this waterway.
Investigations during the project showed that while some characteristics of the Broadwater are
generally indicative of eutrophication, others are typical of mesotrophic waterways. Most
signs of eutrophication in the Broadwater are associated with periods of high inflow when a
NSW Department of Infrastructure, Planning and Natural Resources II