ALGAL BLOOM DYNAMICS IN THE ESTUARINE LAKES

Publication SR4

February 2004

Authors: Andy Stephens, Neil Biggins EPA Marine Sciences Unit and Steve Brett, Microalgal Services

1. INTRODUCTION Water quality conditions for the before and after the flood are presented in this Planktonic algal blooms are a major feature of the report together with information on the biological activity in the Gippsland Lakes and toxic identification of the main dinoflagellate bloom blue-green algal blooms, in particular, are of on- species. A linked sequence of events over a 17 going concern due to their deleterious effects on fish month period is described that progresses from and other marine life, water quality for swimming drought to flood to dinoflagellate bloom and and flow-on impacts on local businesses and ultimately a bloom of the toxic blue/green alga tourism. There are other groups of plankton that Nodularia spumigena. The results of this study have the potential to be toxic and/or disrupt support the proposition that major rain events drive ecosystem function, however little attention has the cycle of algal blooms in the estuarine Gippsland been paid to these in the past. Lakes system. In August 1998 regular EPA “fixed site” water quality sampling and real-time spatial monitoring 2. METHODS techniques detected extremely high levels of Chlorophyll a due to a significant dinoflagellate EPA regularly assesses the Gippsland Lakes at five bloom. The bloom covered much of Lake sites as part of its fixed site monitoring program and Lake King and followed a drought-breaking which has provided a temporal sequence of water flood. Subsequent sampling by EPA followed the quality data since 1986. In addition to this program, course of the bloom and the ensuing development EPA has developed and trialed a system to map the of a bloom of the blue/green alga Nodularia patterns of surface water quality parameters over spumigena. open water areas. This provides more spatially intensive data that can lead to a better The dinoflagellate bloom went largely unnoticed by understanding of the dynamics of significant the wider community, as there were no bright green environmental events. surface scums that are a feature of blue/green Nodularia blooms which have occurred in the area. During the dinoflagellate bloom the water was a dark olive green progressing to a turbid chocolate brown at the height of the bloom.

ALGAL BLOOM DYNAMICS IN THE ESTUARINE GIPPSLAND LAKES

Figure 1. Gippsland Lakes showing EPA water quality monitoring sites

Sampling for this report was conducted over a narrow channel linking the lakes with the sea is seventeen-month period from January 1998 to May maintained through the sand barrier at Lakes 1999. Fixed sites and open water transects were Entrance. The surface area of the lakes system is sampled on eleven occasions mostly at 2 monthly approximately 360 km2 and the catchment about intervals, although more frequent sampling was 20,000 km2 (Bird 1978). carried out at the peak of the dinoflagellate bloom. 2.2 Fixed Site Monitoring 2.1 Study Area At the five EPA water quality monitoring sites (Fig. 1), The Gippsland Lakes, 200km east of Melbourne, is unfiltered water samples for laboratory analysis are an estuarine coastal lagoon system separated by taken. Surface waters are sampled at 0.5 metres and sand barriers from oceanic (Fig.1). From bottom waters at 0.5 metres from the bottom. west to east, the system comprises Lake Wellington, Nutrients are analysed by the Marine and Freshwater which connects to Lake Victoria via the narrow Resources Institute, Queenscliff. Ammonium, nitrate McLennan Strait, Lake King that merges with the and nitrite nitrogen is analysed using colorimetry by eastern end of Lake Victoria near Raymond Island, segmented flow analyser, and total phosphorus with and Reeves Channel which links the system to acid digestion and colorimetry by segmented flow Cunningham and North Arms at Lakes Entrance. A

EPA Victoria 2 ALGAL BLOOM DYNAMICS IN THE ESTUARINE GIPPSLAND LAKES

analyser. Chlorophyll pigments are analysed by approximately 1200 metres. As the contour solvent extraction followed by spectrophotometry. boundaries are software derived, the final result is dependent on the interpolation method, settings 2.3 Vertical Profiles and data density. They do however, give a useful indication of spatial chlorophyll a patterns. Settings In addition to the water samples at the five fixed have been chosen to achieve an intuitively sensible sites, vertical profiles of water quality parameters result and areas that are well away from the including salinity, turbidity and dissolved oxygen sampling zone have been masked. combined with depth are measured with a Yeo-Kal Model 611 water quality meter logging directly to computer. 3. RESULTS

2.4 Water Quality Mapping System 3.1 Sequence of Events Using a water pick-up tube suspended below a Results of spatial and fixed site water quality moving boat, water is directed through a Turner sampling prior to, during and after a major flood, Model 10-005R fluorometer (for chlorophyll a) and combined with rainfall and river flow data, show the through a flow-through cell housing a Yeo-Kal Model development and demise of subsequent algal 611 multi-parameter water quality meter measuring blooms. salinity, temperature, pH, dissolved oxygen and turbidity. By utilising GPS position fixing in Drought conjunction with a laptop computer logging system The Gippsland region experienced a drought based on ‘TerraScan’ (Resource Industry Associates) throughout 1997 to June 1998. From April 1997 to and ‘Excel’ (Microsoft ) software, these water quality June 1998, phytoplankton levels in the lakes system, parameters are measured, recorded and displayed as indicated by chlorophyll a, were relatively low (eg in real time every 4 seconds at boat speeds in Jan – May, Fig. 4). Salinities were high, stratification excess of 30 knots. This allows spatial coverage was usually weak and dissolved oxygen levels in across the lakes system together with the fixed site bottom waters were generally good (eg. 14 May, Fig. sampling within a day. 6). In each transect, a number of samples are taken for Flood laboratory spectrophotometric chlorophyll a analysis to establish a correlation with fluorescence In late June 1998, a major rain event in the as measured in the field by the fluorometer. Gippsland Lakes catchment (Fig. 2) led to flooding on the Mitchell, Nicholson and Tambo Rivers which Generalised spatially interpolated contour plots of combined to cause flooding in the Gippsland Lakes. chlorophyll a are created in the surface mapping At that time the was not significantly system ‘Surfer” (Golden Software Inc.) using kriging affected however the Avon and Perry Rivers were the as the interpolation method and a grid dimension of

Scientific Report 3 ALGAL BLOOM DYNAMICS IN THE ESTUARINE GIPPSLAND LAKES

source of elevated flows into Lake Wellington (Fig. passing over the more saline water below (Fig. 6). It 3). is interesting to note that, even in such an extreme flood event, the incoming waters did not mix When sampling was conducted on 1-2 July 1998, significantly with the deeper layers. This situation salinities in surface waters of the lakes had reduced created strong salinity stratification of the water markedly. However, the floodwaters were restricted column. to the upper 3 to 4 metres of the water column,

120 Noojee Latrobe River Catchment 100 Eas t Sale

Avon River Stratford 80 Catchment Valencia Creek

Dargo 60 Mitchell River Cat chment Bairnsdale 40

24 Hour Rainfall - mm Swifts Creek Catchment 20 Bruthen Nicholson River Nicholson 0 Cat chment 21-Jun 22-Jun 23-Jun 24-Jun 25-Jun 26-Jun Source: Bureau of Meteorology 1998

Figure 2. Indicative 24 hour Rainfall for the Gippsland Lakes Catchment

EPA Victoria 4 ALGAL BLOOM DYNAMICS IN THE ESTUARINE GIPPSLAND LAKES

90000

80000 Nicholson R at Deptford Mitchell R at Glenaladale 70000 Avon R at Stratford Latrobe R Combined T ambo R D/S Ramrod Ck 60000

50000

40000

Mean Daily Flow - ml/d 30000

20000

10000

0 6-Jul 1-Jun 8-Jun 7-Sep 13-Jul 20-Jul 27-Jul 3-Aug 15-Jun 22-Jun 29-Jun 14-Sep 21-Sep 28-Sep 10-Aug 17-Aug 24-Aug 31-Aug

Figure 3. River Flows to the Gippsland Lakes - June to Sept 1998

During the July 1998 sampling, phytoplankton levels about 4 psu immediately after the flood. A were relatively low in Lake King and most of Lake dinoflagellate bloom had developed over much of Victoria. However, an area of elevated chlorophyll a Lake King and Lake Victoria (Figure 4). The main was detected in the southwest corner of Lake bloom species were Heterocapsa triquetra and to a Wellington due to a localised bloom of the non-toxic lesser extent Gymnodinium cf aureolum, and dinoflagellate Heterocapsa triquetra. A small bloom significant numbers of the small diatom of this species had been detected previously off the Skeletonema costatum also were recorded. However, eastern entrance to McLennan Strait on 14 May at the next sampling time on 20 August, G. cf 1998. aureolum was by far the most dominant organism and chlorophyll a levels exceeded 1000 µg/l at Dinoflagellate Bloom some locations. By the next sampling time on 5 August, salinities in surface waters at the Lake King North site had risen back to about 16 practical salinity units (psu) from

Scientific Report 5 ALGAL BLOOM DYNAMICS IN THE ESTUARINE GIPPSLAND LAKES

Decline of the Dinoflagellate Bloom By the next sampling time on 25-26 November chlorophyll a levels in Lake King and the eastern end The bloom had started to diminish by 24 September of Lake Victoria had returned to near pre-flood with chlorophyll a levels in Lake King below 40 µg/l. levels. However, levels in Lake Wellington and Numbers of G. cf aureolum and Skeletonema western Lake Victoria were declining at a slower rate costatum had decreased substantially although and remained elevated. large numbers of nano and picoplanktonic organisms were present. It should be noted that from previous observations chlorophyll a levels in the shallow and turbid Lake Another rain event occurred in late September 1998 Wellington are typically higher than in the other leading to flooding on the Mitchell River (BoM lakes. The plankton in Lake Wellington are usually of September 1998) and elevated flows in the Latrobe mixed groups and species with a high proportion of River (Figure 3). The September sampling was nano and picoplankton making identification conducted just prior to any impact from this event. difficult.

EPA Victoria 6 ALGAL BLOOM DYNAMICS IN THE ESTUARINE GIPPSLAND LAKES

Figure 4. Spatially Interpolated Chlorophyll a Contours – 1998 Scientific Report 7 ALGAL BLOOM DYNAMICS IN THE ESTUARINE GIPPSLAND LAKES

Blue/Green Algal Bloom Channel near Metung were the areas most affected. Extremely high cell counts were recorded at In mid January 1999, the first sighting of a bloom of localised sites particularly near Metung (K. Thomas the blue/green alga Nodularia spumagena was pers. comm.) but by April 1999 no sign of the reported. Lake King and Bancroft Bay and Reeves Nodularia bloom was apparent.

Figure 5. Spatially Interpolated Chlorophyll a Contours Feb to May 1999

EPA Victoria 8 ALGAL BLOOM DYNAMICS IN THE ESTUARINE GIPPSLAND LAKES

3.2 Water Quality Conditions significantly clearer demonstrating the lack of mixing between the two layers. 3.3 3.2.1 Vertical Profiles of Physico- chemical Water Quality Indicators at Lake King 5 August 1998 – Early stages of the bloom North Strong stratification continued. Salinity increased to Differences in the vertical profiles of selected 16 psu in the surface layer and increased only physico-chemical parameters over time illustrate the slightly to about 30 psu in the lower layer. Turbidity impact of the flood on water quality. The Lake King had dropped significantly in the surface layer down North site was selected to demonstrate the changes to 3 ntu and the lower layer still close to 0 ntu. in water quality in terms of turbidity, salinity and Dissolved oxygen in the surface layer was dissolved oxygen in the bloom area over time. These supersaturated probably reflecting the very high patterns are illustrated in Figure 6. This site is productivity of the dense dinoflagellate bloom. This relatively deep at around 7 metres, and is more contrasts with severe oxygen depletion in the lower central to Lake King and thus not as affected by layer where saturation levels were less than 10%. shoreline or tidal influences as other sites in the 24 September 1998 – Later stages of the bloom bloom area. The salinity profile for September was similar to that 14 May 1998 – Six weeks prior to the flood in August except that the transition between the The vertical profile of salinity showed the lake to be upper, fresher layer and the lower, more saline layer very saline (around 32 psu) and well mixed showing was much sharper indicating strong stratification no stratification. Dissolved oxygen levels were about and stable conditions. The turbidity profile was also 100% saturated through most of the water column similar to the August sampling. Oxygen levels in the with only a slight depression close to the bottom. surface layer still showed a degree of Turbidity was close to zero throughout the water supersaturation but not as extreme as in August, column. which suggests a reduction in bloom productivity. However, the bottom layer was anoxic with the 1 July 1998 – One week into the flood oxygen saturation level passing from 110% at the A distinct freshwater layer (salinity of 4 psu) surface to 0% at about 2 metres above the bottom. extended down to about 3 metres and overlayed quite saline bottom waters at 28 psu. Although the water column was now stratified, dissolved oxygen levels were still relatively high, generally above 80% saturation, in the bottom layer. Turbidity was very high in the surface layer due to the turbid floodwaters. However, the lower saline layer was

Scientific Report 9 ALGAL BLOOM DYNAMICS IN THE ESTUARINE GIPPSLAND LAKES

14-May 1-Jul 5-Aug 24-Sep

Turbidity - ntu 0 5 10 15 20 25 30 35 40 45 50 0

2

4

6 Depth - metres

8

Salinity - psu 0 5 10 15 20 25 30 35 40 0

2

4

6 Depth - metres

8

Dissolved Oxygen - % saturation 0 20 40 60 80 100 120 140 0

2

4

6 Depth - metres

8

Figure 6. Vertical Profiles of Turbidity, Salinity and Dissolved Oxygen Lake King North Site, May to September 1998 EPA Victoria 10 ALGAL BLOOM DYNAMICS IN THE ESTUARINE GIPPSLAND LAKES

3.2.2 Nutrients King in January and at Metung in February due to the Nodularia bloom. Lake Wellington and most of Lake On 1 July, one week after the start of the flood, Victoria were not affected by the Nodularia bloom. dissolved inorganic nitrogen (DIN) levels were extremely elevated at Lake King North, Lake King The bloom density varied significantly across the South and Metung, the sites most affected by the study area. From the spatial mapping data on 20 flood (Fig. 7). However by 5 August, levels in surface August 1998, chlorophyll a levels ranged from 10 to waters were down to near pre-flood levels. The other 1300µg/l over the area affected by the dinoflagellate sites sampled showed a similar pattern of change bloom. No fixed site sampling was conducted on but at lower DIN levels. Lake Wellington, least this date. The highest chlorophyll a level recorded in affected by the flood, showed the smallest pulse of the fixed site sampling program was 115 µg/l at nitrogen. At the Lake King sites, DIN in bottom Metung on 5 August, when spatially mapped waters remained elevated after the flood. chlorophyll a measurements ranged from 25 to 250

Total phosphorus (PTOT) levels in the lakes µg/l. appeared not to rise as an immediate result of the The highest chlorophyll a concentrations due to the flood (Fig. 7). PTOT levels in bottom waters at the Nodularia bloom were recorded on 18 March 1999 Lake King sites did rise significantly towards the end by spatial mapping. Levels ranged from 10 to 400 of the bloom about three months after the flood. At µg/l over the affected area compared with the the Lake Wellington and Lake Victoria sites, highest measurement from the fixed site program of phosphorus levels also increased well after the 19 µg/l at the Metung site on the same date. The flood event but were similar in the surface and highest fixed site chlorophyll a result due to the bottom waters, probably due to less pronounced Nodularia bloom was 26 µg/l on 17 February at the salinity stratification (Fig. 7). Lake King North site when the spatially mapped

The phosphorus pattern at the Metung site shows results ranged from 3 to 62µg/l. higher levels in surface waters for the July to The differences between these results highlight the November 1998 period. This is most probably due to value of the spatially intensive mapping system to the bottom waters at this site being more directly better characterise water quality parameters that influenced by oceanic tidal water from Bass Strait. can be highly variable. Traditional water sampling at discrete fixed sites that are often far apart can miss 3.2.3 Chlorophyll a much of the detail of events such as algal blooms Over the July to August period, phytoplankton and floods. biomass increased dramatically in Lakes King and Victoria as indicated by chlorophyll a levels (Fig. 7). By November 1998 chlorophyll a levels had reduced significantly, but then rose again slightly in Lake

Scientific Report 11 ALGAL BLOOM DYNAMICS IN THE ESTUARINE GIPPSLAND LAKES

Total Phosphorus (PTOT) - ug/l Dissolved Inorganic Nitrogen (DIN) - ug/l Chlorophyll a (Chl a)- ug/l Salinity - psu PTOT Sur f ac e PTOT Bottom DIN Surf ace DIN Bottom Chl a - Surface 1m Salinity - Surf ace Salinity - Bottom

Lake King North Surface 0.5m - Bottom 7m

1000 35 250 40 30 800 200 30 25 150 600 20 20 15 100 400 10 10 200 50 5 0 0 0 0

r y v r 9 9 8 ly pt ar 9 9 9 9 a u e o Ma n Ma M J Aug N M y 9 n Feb 6 4 2 5 5 a 6 2 July5 Aug 7 Ja 2 18 2 14 May 25 Nov Ja 1 18 Mar 1 24 S 2 17 Feb M 24 Sept 1 4 0 14 Jan 98 2 20 May 1 21 Jan 99 2

Lake King South Surface 0.5m - Bottom 7m

250 40 1000 35 200 30 30 800 25 150 600 20 20 100 400 15 10 10 50 200 5 0 0 0 0

r y 98 ar ay ug 99 ar 98 ept ov A Feb M Ma Ma S N an 2 July 5 an 2 July 5 Aug Jan 99 J 26 M 14 M 24 Sept25 Nov 17 18 26 14 24 25 17 Feb 18 Mar May 99 14 21 J 20 May 99 14 Jan 21 20

Metung Surface 0.5m - Bottom 12m

250 140 1000 35 120 30 200 800 100 25 150 80 600 20 100 60 400 15

40 DIN - ug/l Chl A - ug/l - A Chl

PTOT - ug/l PTOT - 10 50 Salinity - psu 20 200 5 0 0 0 0

8 y r 9 a pt a 8 t v 9 eb 9 9 o eb Mar Aug Se F ep 99 F Mar an 6 8 M ay n Mar Aug n 4 M 2 July5 4 a 6 2 July 5 7 8 2 1 25 Nov Jan 9917 1 M J 2 14 May 4 S 25 N 1 1 4 J 2 1 4 2 1 2 20 1 21 Ja 20 May 99

Lake Victoria Surface 0.5m - Bottom 5m 250 80 500 35 30 200 400 60 25 150 300 20 40 100 200 15 20 10 50 100 5 0 0 0 0

y 99 ar 99 99 ar 99 a ug Feb M ug Feb M July A July A 2 5 ay 2 5 ay 26 Mar14 M 24 Sept25 Nov Jan 17 18 M 26 Mar 14 May 24 Sept25 Nov Jan 17 18 M 14 Jan 98 21 20 14 Jan 98 21 20

Lake Wellington Surface 0.5m - Bottom 3m

250 80 500 35 30 200 400 60 25 150 300 20 40 15 100 200 10 20 50 100 5

0 0 0 0

ar 9 ug 99 ar ug 99 9 July Feb M July Feb M May A Sept an 98 2 A an an 98 2 5 4 an J 26 Mar 5 25 Nov 17 18 J 26 Mar14 2 25 Nov 17 18 14 May 24 Sept 14 21 J 14 21 J 20 May 99 20 May

Figure 7. Nutrient, Chlorophyll a and Salinity data for the Lake Wellington, Lake Victoria, Lake King and Metung Sites EPA Victoria 12 ALGAL BLOOM DYNAMICS IN THE ESTUARINE GIPPSLAND LAKES

3.3 Identification of Species Gymnodinium species (egs. Bolch & Hallegraeff 1990, Bolch et al. in press, Ellegaard et al 1993, There were two distinct dinoflagellates that Ellegaard & Yoshima 1998) including the Paralytic dominated the phytoplankton during the study. Shellfish Poison (PSP) producing Gymnodinium Detailed examination and identification of the catenatum. The overall features and dimensions of dinoflagellates was necessary to determine if either the dinoflagellate fit within the description of of these organisms was known to be toxic, and to Gymnodinium aureolum (see Hansen et al) so we enable accurate comparisons should future blooms have ascribed the name Gymnodinium cf. aureolum occur. to the organism in this study. Knowledge of the The most abundant dinoflagellate, a non-chain- toxicity of G. aureolum is somewhat confused as G. forming gymnodinioid cell, reached levels in excess mikimotoi, a known fish killer, has often been of 3x107 cells /L. The cells, which were 24-34 µm in misidentified as G. aureolum (Hansen et al). G. cf length and 22-30µm wide, contained numerous aureolum from this study may well prove not to be golden-brown chloroplasts and a central to posterior toxic as no fishkills were reported at the time of the nucleus. Scanning Electron Microscopy (SEM) bloom however, in light of its close affinity with revealed the presence of a loop (or horseshoe) known toxic species, further investigation into its shaped apical groove, a feature common to a range toxicity is warranted. of

Figure 8 . Scanning electron micrographs of Gymnodinium cf. aureolum from this study

Scientific Report 13 ALGAL BLOOM DYNAMICS IN THE ESTUARINE GIPPSLAND LAKES

The other important dinoflagellate dominated during the early stages of the bloom, reaching densities in excess of 9x106 cells/L. Cells were between 22 and 30µm in length and possessed a distinctive antapical horn, characteristic of Heterocapsa triquetra. Thecal plate arrangement and scale morphology were examined with Transmission Electron Microscopy (TEM) and SEM to verify the identification of this organism. Heterocapsa triquetra has a worldwide distribution and is not known to be toxic.

Figure 9. Scanning electron micrograph of Heterocapsa triquetra

EPA Victoria 14 ALGAL BLOOM DYNAMICS IN THE ESTUARINE GIPPSLAND LAKES

4. DISCUSSION There have been floods to the Gippsland Lakes that did not appear to be followed by major algal blooms (Chessman 1988). For example, chlorophyll data 4.1 Factors Influencing Dinoflagellate Bloom held by EPA and that reported in Arnott and Formation and Dynamics McKinnon (1983) suggests that no major bloom 4.1.1 Catchment run-off occurred in the spring or summer of 1978/79 following the major floods of June 1978. A review of algal blooms in Australian coastal waters indicated that dense algal concentrations are most The nature of antecedent conditions and river flows strongly developed under stratified stable appears to be important in promoting algal blooms conditions, at high temperatures and following high in the Gippsland Lakes. Long dry periods with low organic input from land run-off after heavy rains river flows during autumn and winter, followed by (Hallegraeff, 1995). These conditions were apparent major rainfall events and flood flows in spring, in this study, except temperatures were not at a appear to be typical conditions associated with algal maximum in August 1998 when the bloom was blooms. detected. Previous reports (Longmore, 1994, Norman, 1988) indicate that blooms in the Gippsland Lakes can happen at any time of year suggesting that temperature may not necessarily be a critical factor as to whether a bloom develops.

Longmore (1994) reported a dinoflagellate/diatom bloom in the Gippsland Lakes following heavy rains in November 1988 with the dominant organism being an “unknown” dinoflagellate. It is interesting to note that this bloom preceded a blue/green algal Nodularia bloom in July 1989.

The relationship between other flood events and algal blooms in the Gippsland Lakes further highlights the potential link with catchment run-off. Table 1 outlines these events from 1965 to 1997 and although some blooms may have gone unreported the list covers most of the major blooms for the period. Dates of blooms in the table reflect when blooms were reported, not necessarily when they started.

Scientific Report 15 ALGAL BLOOM DYNAMICS IN THE ESTUARINE GIPPSLAND LAKES

Table 1. Reports of Blooms and Flood Events in the Gippsland Lakes - 1965 to 1997

1965 July 1965 - Nodularia bloom in Lake Wellington after bushfires and heavy rain (Solly 1966)

1971 Jan/Feb 1971 - major flood in Gippsland Lakes (Bird 1972)

March 1971 - Microcystis bloom in Lake Wellington (F&WD 1971)

May 1971 - Lake King, dinoflagellate dominated

- Lake Victoria, mainly diatom dominated - Nodularia present

- Lake Wellington, Nodularia/diatom dominated

- Nodularia dominant in Bunga Arm (Powling and Wan)

1973/74 Aug 1973 - major flooding on Latrobe, Macalister and Mitchell Rivers (BoM)

Feb 1974 - Nodularia bloom Lakes King and Victoria (EPA 1974)

1984 July 1984 - moderate flooding on Mitchell, Tambo and Latrobe Rivers Floods (BoM)

Oct 1984 - minor non-specified bloom in Lakes Victoria and Wellington (chlorophyll data in Longmore et al 1988)

1985/86 Sept/Oct 1985 - floods on Latrobe and Mitchell Rivers (BoM)

Dec 1985 -major flooding on Tambo river and moderate on Latrobe and Mitchell rivers (BoM)

Jan 1986 - Anabaena bloom in Lake King (Norman 1988)

1986/87 Oct 1986 - minor flooding on Macalister and Mitchell Rivers (BoM)

Feb 1987 - Nodularia bloom in Lake King (Norman 1988)

1987 July 1987 - minor flooding on Mitchell and Thompson Rivers (BoM)

Aug 1987 - non-specified bloom in Lake Victoria (Norman 1988)

Dec 1987 to - Nodularia bloom in Lake Victoria ( Norman 1988)

April 1988

EPA Victoria 16 ALGAL BLOOM DYNAMICS IN THE ESTUARINE GIPPSLAND LAKES

1988/89 Nov 1988 - has wettest November on record, moderate flooding on the Mitchell River (BoM)

Dec1988 - dinoflagellate bloom in Lake Victoria (Longmore 1994)

July 1989 - Nodularia bloom in lakes (Longmore 1994)

1989 July 1989 - Minor flooding on Latrobe River (BoM)

Dec 1989 - Nodularia bloom in east Lake Victoria and south Lake King (Longmore 1994)

1990 April 1990 - major flooding on Mitchell, Avon and Thompson Rivers, minor to moderate flooding on other rivers (RWC 1991)

July 1990 - unspecified bloom in Lake King North (EPA chlorophyll data)

Sept 1990 - unspecified bloom in lakes King South and Victoria

(EPA chlorophyll data)

1992/93 Sept 1992 - record breaking rains and many floods across Victoria (BoM)

Dec 1992 - major flooding on the Macalister River (BoM)

Jan 1993 - Microcystis bloom in Jones Bay/Lake King (P Marwood pers. com.)

1995/6 October 1995 - major flooding on the Latrobe River (BoM)

January 1996 - unspecified bloom (not blue/green) in Lake Victoria

(EPA chlorophyll data)

May 1996 - Nodularia bloom in Lake King (EPA data)

1996/7 July-Oct 1996 - minor flooding on the Latrobe and moderate flooding on Mitchell Rivers (BoM)

Feb 1997 - Nodularia bloom in Lake King (EPA chlorophyll data)

Scientific Report 17 ALGAL BLOOM DYNAMICS IN THE ESTUARINE GIPPSLAND LAKES

al. (1999) found that after input into Tuggerah Lakes, 4.1.2 Nitrogen and Phosphorus New South Wales, from a major rain event, there was Phytoplankton productivity in the Gippsland Lakes little change in phosphorus concentrations but an is considered to be primarily nitrogen limited increase in dissolved nitrogen and a rapid increase (Axelrad and Bulthuis 1977, Smith 1975). The levels in chlorophyll a concentrations. of nitrogen measured in the first half of 1998 were at the lower end of the normal range. When sampling 4.1.3 Organic Matter was conducted on 1 July, one week after the rain Phytoplankton blooms often occur after significant event, dissolved inorganic nitrogen (DIN) levels were rain events and river discharge which introduce extremely elevated. However, by the next sampling large quantities of humic substances (dissolved time on 5 August, levels in surface waters were down organic matter) to estuarine and coastal systems to near pre-flood levels. This was particularly evident (Heil, 1996). Nitrogen in combination with humic at the Lake King North, Lake King South and Metung substances from soils, rivers, sediments and sites. The other sites showed similar patterns (Fig. 7) decomposing vegetation can stimulate the growth of with Lake Wellington, which was least affected by dinoflagellates to the point of out competing the flood, showing the smallest pulse of nitrogen. diatoms (Graneli et al. 1989). Doblin (1999) found Over this period, phytoplankton biomass increased that the input of dissolved organic matter into dramatically in Lakes King and Victoria as indicated Tasmanian coastal waters after rainfall events by chlorophyll a levels (Figs. 4&7). Rapid played a critical role in the development of blooms assimilation of DIN from the water column by of Gymnodinium catenatum a potentially closely phytoplankton most likely accounted for the related species to the Gymnodinium sp. of this lowering of DIN concentrations. This pattern is study. consistent with observations from other Australian Although humic substances are not analysed in the estuaries (eg. O'Donohue and Dennison 1997). current Gippsland Lakes monitoring program it is In contrast to DIN, total phosphorus (PTOT) levels most probable that elevated levels would have been appeared not to rise as an immediate result of the associated with the flood. As a result of low river flood. However, PTOT levels did rise significantly, flows prior to the June rain event, organic matter particularly in bottom waters, towards the end of the would be retained in the catchment. A "first flush" bloom about three months later. (Fig. 7). Two factors from the major rain event is likely to be particularly could explain this rise in phosphorus - firstly, high in dissolved organic matter and could play a enhanced phosphorus release from the sediments part in bloom initiation and maintenance. due to oxygen depletion in bottom waters and 4.1.4 Other Micro-nutrients and Trace Elements secondly, release of phosphorus from decaying bloom organisms. Levels of some trace elements can be critical for determining the cell densities that phytoplankton It has been reported elsewhere that phosphorus did bloom species can achieve. Iron (Fe) and Selenium not increase as a result of a flood event. Scanes et

EPA Victoria 18 ALGAL BLOOM DYNAMICS IN THE ESTUARINE GIPPSLAND LAKES

(Se) are two such elements although it is unlikely thus stratifying the previously well-mixed water that iron is limiting in an estuarine system such as column. Salinity stratification, in combination with the Gippsland Lakes. the increased organic sediment load from the bloom, led to severe oxygen depletion in the lower Selenium has been identified as an important trace layer and by 24 September at the Lake King North element for the growth of certain phytoplankton site the lower 1.5 metres of the water column was species such as the dinoflagellates Gymnodinium anoxic. This was towards the later stages of the catenatum (Doblin et al. 1999) and Gymnodinium bloom and appears to have led to a significant nagasakiense (mikimotoi) (Ishimaru et al. 1989). release of phosphorus from the sediments. These species are closely related to Gymnodinium cf aureolum found in this study so it is possible that 4.1.6 Species Identification selenium plays a role in the growth of Particular attention was paid to the identification of dinoflagellates in the Gippsland Lakes. the bloom species to determine whether they were Doblin et al. (1999) conclude that the riverine input known to be toxic and also to enable comparisons of inorganic selenium and its interaction with to be made should such blooms continue to be a dissolved inorganic matter may be a critical factor in regular occurrence in the Gippsland Lakes. the development of G. catenatum blooms after rain. Identification of plankton species, especially The level of selenium in the lakes is not known, unarmoured dinoflagellates, can be difficult. however, Glover et al. (1980) reported elevated Because of the delicacy of many species, the cells levels in fish. An assessment of the significance of do not usually retain their morphology when selenium to algal blooms in the Gippsland Lakes preserved by normal means and identification may be warranted. generally requires careful observations of live cells It is reported in the scientific literature that blooms (Larson 1994). With some species electron of dinoflagellates can be related to levels of microscopy may be necessary to reveal the fine cobalamin (vitamin B ) that is washed from soils 12 detail necessary for identification. and marsh areas where it is produced by both The taxonomic resolution of previous studies in the bacteria and blue-green algae (Round 1965). Once Gippsland Lakes (eg. Smith 1975, Ducker et al 1977, again, the significance of this substance to bloom Longmore 1994) were often limited to genus level dynamics in the Gippsland Lakes is not known but and did not include detailed descriptions of could be a useful avenue for future study. organisms. Consequently it is not known whether 4.1.5 Stratification the bloom species in this study have been a feature of previous blooms. A surprising aspect of the flood event was that the huge quantities of fresh water discharging into the lakes did not push out the deeper saline waters. The floodwater was restricted to the top 3 to 4 metres

Scientific Report 19 ALGAL BLOOM DYNAMICS IN THE ESTUARINE GIPPSLAND LAKES

4.2 Development of the blue/green algal • Dinoflagellate bloom diminishes. bloom • A second, smaller rain event in late Blue-green algal blooms are usually associated with September 1998 added more fresh water to freshwater systems where phosphorus is generally the system the limiting nutrient. In the Baltic Sea, where • Salinity stratification resulting from Nodularia blooms are a persistent problem, bloom freshwater pulse, and increased organic development is initiated through phosphorus load on sediments from senesing enrichment of warm, stratified surface waters low in dinoflagellate/diatom bloom, led to anoxia nitrogen (Sellner 1997). in bottom waters. In the Western Australian Peel-Harvey estuarine • Phosphorus released from sediments system winter and spring diatom blooms developed during anoxic conditions, and additional following nutrient loading from significant river phosphorus released from the senesing inflow (Lukatelich and McComb 1986). After the dinoflagellate bloom. collapse of the diatom blooms, recycling of nutrients Strong winds late in December 1998 supported summer blooms of Nodularia. Similar • (Grayson et al. 1999) caused mixing of processes could be occurring in the Gippsland nutrient rich bottom waters with warmer Lakes. surface water in the euphotic zone. It seems likely that the dinoflagellate bloom reported in this study modified conditions in the • Low N and high P coupled with warmer Lakes in such a way as to favour the later water and favourable salinity led to serious bloom - January/March 1999. development of the Nodularia bloom. The following Nodularia sequence of events is hypothesised to have led Preliminary monitoring for this study suggests that a ultimately to the Nodularia bloom that started in similar scenario may have preceded a previous January 1999. Nodularia bloom in the Gippsland Lakes. Heavy spring rains in October 1995 and major flooding in • Prolonged drought resulted in lakes the Latrobe River followed a winter of below average relatively saline and well mixed. rainfall. A large area of elevated chlorophyll a, • Major rain event in June 1998 (especially in possibly due to a dinoflagellate/diatom bloom, was lower catchment and eastern end of Lakes). detected in Lake Victoria in January 1996 and a

• Pulse of nitrogen and possibly other growth Nodularia bloom was well established by May 1996. promoters from rivers and catchment. As discussed previously, Longmore (1994) also reported a Nodularia bloom in July 1989 that • Major dinoflagellate/diatom bloom in followed a dinoflagellate bloom in December 1988 July/August 1998 and heavy November rains. • Nitrogen and possibly other growth promoters depleted.

EPA Victoria 20 ALGAL BLOOM DYNAMICS IN THE ESTUARINE GIPPSLAND LAKES

It appears that it can take a lag of six months or special acknowledgment goes to Sean Walsh whose more for a rain event to lead to a major blue/green software prowess and persistence has made the algae bloom in the Gippsland Lakes. The logging system possible. Valuable assistance with development of such blooms may be dependent on software was also provided by Elvin Slavic of the progress of other types of blooms such as, in Terrasolutions, and Terry Boyd and Geoff Bailey from this case, the dinoflagellates. There may well be Resource Industry Associates. other scenarios that result in blue /green algal blooms but further regular monitoring and special 7. REFERENCES investigations are required to fully understand this large and complex system. Arnott, G.H. and McKinnon, A.D. (1983). The zooplankton communities of the Gippsland Lakes from 1978 to March 1980. Internal report No.51, 5. CONCLUSIONS Ministry for Conservation, Fisheries and Wildlife A major rain episode in June 1998 and consequent Division, 43pp. flooding of the Gippsland Lakes initiated a sequence Axelrad, D.M. and Bulthuis, D.A. (1977). of events that included a significant dinoflagellate Phytoplankton nutrient limitation in the Gippsland bloom and culminated in a bloom of the toxic Lakes. Paper No. 145 Environmental Studies Series, blue/green alga Nodularia spumigena. Ministry for Conservation, Victoria Elevated nitrogen levels associated with the flood Bird. E.C.F. (1972). The effects of the 1971 Floods on appeared to initiate the dinoflagellate bloom, the the Gippsland Lakes. Journal of the Geography result of which was to modify conditions that Teachers' Association of Victoria, Vol.12, No.1: 20- favoured the development of the blue/green algal 28. bloom. Bird, E.C.F. (1978). The geomorphology of the Gippsland Lakes. Publication No. 186 Environmental 6. ACKNOWLEDGMENTS Studies Series, Ministry for Conservation, Victoria

Acknowledgment is gratefully given to the Bureau of Bolch, C.J. and Hallegraeff, G.M. (1990). Meteorology, Melbourne for rainfall data, Ross Scott, Dinoflagellate cysts in recent marine sediments from Catchment Authority, and Thiess Tasmania, . Botanica Marina 33 : 173-92. Environmental for river flow data and Gus Fabris and Bolch, C.J., Negri, A.P. and Hallegraeff, G.M. (In staff at MAFRI for analytical services. Thanks for Press) Gymnodinium microreticulatum sp. nov. advice and editorial comment go to Jo Klemke and (Dinophyceae): a naked, microreticulate cyst Brett Light, EPA Marine Sciences and Vicki Brown, producing dinoflagellate, distinct from Melbourne Water. David Robinson and Peter Gymnodinium catenatum Graham and Gymnodinium Marwood, EPA and Keith Thomas, DNRE Bairnsdale, nolleri Ellegaard et Moestrup. also provided valuable advice and assistance. A

Scientific Report 21 ALGAL BLOOM DYNAMICS IN THE ESTUARINE GIPPSLAND LAKES

BoM. (various months and years) Monthly Weather F&WD (1971). Fisheries and Wildlife Department Review - Victoria. Bureau of Meteorology. memorandum by A. Dunbavin Butcher dated 23 May 1971. Chessman B.C. (1988). The 1987/88 Gippsland Lakes algal bloom. In, Gippsland Lakes Algal bloom Glover, J.W., Bacher, G.J. and Pearce, T.S. (1980). seminar - discussion papers. Department of Gippsland regional environmental study: Heavy Conservation Forests and Lands, Victoria. 38-50. metals in biota and sediments of the Gippsland Lakes. Report No. ESS 279. Environmental Studies Doblin, M.A., Blackburn, S.I. and Hallegraeff, G.M. Division, Ministry for Conservation, Victoria. (1999). Growth and biomass stimulation of the toxic dinoflagellate Gymnodinium catenatum (Graham) by Graneli, E., Olsson, P., Sundstrom, B and Elder, L. dissolved organic substances. J. Exp. Mar. Biol. Ecol. (1989). In situ studies of the effects of humic acids 236, 33-47. on dinoflagellates and diatoms. In: "Red Tides - Biology, Environmental Science and Toxicology" Ducker, S.C., Brown, V.B. and Calder, D.M. (1977). An (Eds T. Okaichi, D.M. Anderson, T. Nemoto), Elsevier, identification of the aquatic vegetation in the New York. 209-212. Gippsland Lakes. Ministry for Conservation, Victoria. Environmental Studies Program. Grayson, R., McMaster, M, and McCowan, A. (1999). Summary of work on the Gippsland Lakes, 1998/9 Ellegaard, M., Christensen, N.F. and Moestrup, O. by the Centre for Environmental Hydrology University (1993). Temperature and salinity effects on growth of of Melbourne. University of Melbourne. 26pp. a non-chain-forming strain of Gymnodinium catenatum (Dinophyceae) established from a cyst Hallegraeff, G.M. (1991). 'Aquaculturists' guide to from recent sediments in The Sound (Oeresund), harmful Australian microalgae.' Fishing Industry Denmark. J. PHYCOL. vol. 29, no. 4, pp. 418-426 Training Board of Tasmania, Hobart. lllpp.

Ellegaard, M. and Oshima, Y. Gymnodinium nolleri Hallegraeff, G.M. (1995). Algal Blooms in Australian (1998) Ellegaard et Moestrup sp. ined. Coastal Waters. Water Vol. 23, No. 3. 20-23. (Dinophyceae) from Danish waters, a new species Hansen, G., Daugbjerg, N. and Henriksen, P. (2000). producing Gymnodinium catenatum-like cysts: Comparative study of Gymnodinium mikimotoi and Molecular and toxicological comparisons with Gymnodinium aureolum, Comb.Nov. (=Gyrodinium Australian and Spanish strains of Gymnodinium aureolum) based on morphology, pigment catenatum. Phycologia, vol. 37, no. 5, pp. 369-378. composition, and molecular data. J. Phycol. 36, 394- EPA (1974). A report on the Gippsland Lakes algal 410. bloom - autumn 1974. Water Quality Branch, Heil, C. (1996). The influence of dissolved humic Environment Protection Authority, Victoria November material (humic,fulvic and hydrophilic acids) on the 1974. ecology of marine phytoplankton. Ph.D. dissertation, University of Rhode Island, Kingston. RI, 483 pp.

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Ishimaru, T., Takeuchi, T., Fukuyo, Y. and Kodama, O'Donohue, M.J.H. and Dennison, W.C. (1997). M. (1989). The selenium requirements of Phytoplankton productivity response to nutrient Gymnodinium nagasakiense. In: "Red Tides - concentrations, light availability and temperature Biology, Environmental Science and Toxicology" along an Australian estuarine gradient. Estuaries (Eds T. Okaichi, D.M. Anderson, T. Nemoto), Elsevier, Vol. 20, No. 3. 521-533 New York. 357-360. Powling J. and Wan H. (1971). Preliminary report of a Larson, J. (1994). Unarmoured dinoflagellates from field survey conducted following the Gippsland Australian waters. I. The genus Gymnodinium Lakes Symposium, Arthur Rylah Institute, 1970. (Gymnodiniales, Dinophyceae). Phycologia 33 (1): Round, F.E. (1965). The Biology of the Algae. Edward 24-33. Arnold (Publishers) LTD. Longmore, A.R. (1994). Nutrient and chlorophyll RWC (1991). Report on Gippsland April 1990 Floods. concentrations in the Gippsland Lakes 1988-89. Rural Water Commission of Victoria. Publication No. 419 Environment Protection Scanes, P., Bourgues, S., Ajani, P., Coade, G. and Authority, Victoria Koop, K. (1999). How do coastal lakes respond to Longmore, A.R., Gibbs C.F. and Marchant J.W. nutrient inputs? Changes in Tuggerah Lakes (1988). Water quality in the Gippsland Lakes, July following a rainfall event. Abstract from A.M.S.A. 1984 - June 1985: spatial and temporal trends. Conference Proceedings, University of Melbourne. Technical Report No. 60 Marine Science Sellner, K.G. (1997). Physiology, ecology, and toxic Laboratories, Dept. of Conservation, Forests & properties of marine cyanobacteria blooms. Limnol. Lands. 71 pp. Oceanogr. 42(5. Part 2): 1089-1104 Lukatelich, R.J. and McComb, A.J. (1986). Nutrient Smith, J. (1975). A water quality study of the levels and the development of diatom and blue- Gippsland Lakes. June 1973 - June 1974. E.P.A. green algal blooms in a shallow Australian estuary. internal report J. Plankton Res. 8: 597-518 Solly, W.W. (1966). A bloom of the alga Nodularia in Morrill, L.C. and Loeblich, A.R. 111 (1981). A survey of Lake Wellington, Victoria, June-July 1965. Australian body scales in dinoflagellates and a revision of Society for Limnology Newsletter, 5, 28-29. Cachonina and Heterocapsa (Pyrrhophyta). Journal of Plankton Research 3: 53-65.

Norman, L. (1988). The 1987/88 Gippsland Lakes algal bloom. In, Gippsland Lakes

Algal bloom seminar - discussion papers. Department of Conservation Forests and Lands, Victoria. 20-25.

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