Dingo Beach

Principal watchers: Geoff Bunn, Margaret Parr, Valerie Bunn, Wendy Galloway & Seagrass-Watch HQ
Occasional and past watchers: Betty Wilson, Carolyn Williams, Dianne Turner, Jean Wells & Joyce Patullo
Location: Intertidal sand flats in north facing mainland bay, in the north of the region
Site codes: DB1 & DB2
Issues: Urban expansion, sewage and groundwater, siltation due to clearing and erosion
Comments: Turtle and fish feeding grounds

Status (Feb05):

• Dingo Beach meadows cover approximately 55ha, which are predominately Halodule uninervis with Halophila ovalis. Other species (including Thalassia hemprichii, Syringodium isoetifolium and Cymodocea serrulata) are present within the bay. The seagrass species composition has remained relatively stable over the monitoring period, indicative of natural and/or anthropogenic disturbance.
• The seagrass cover is generally moderate (5-30%). Seagrass abundance generally follows a seasonal trend, characterised by maximum cover (>20% cover) in summer/autumn (December –April) and minimum cover (<20% cover) in winter (June-July). This suggests that seagrass meadows at these sites are primarily influenced by natural factors (temperature, light, wave action).
• At Dingo Beach maximum epiphyte cover (>35-75%) occurred in summer (December) and autumn (March), and minima in winter. Algal cover remained below 20% with no seasonal pattern. High epiphyte cover in spring-summer may have been caused by high water temperatures and light availability. High rainfall during summer may also enrich waters with nutrients necessary for epiphyte growth.
• Gastropods, hermit crabs and polychaete worms were abundant at Dingo Beach. The high abundance of invertebrate fauna at these sites suggested that seagrass provides an adequate supply of detritus, grazing matter and faunal prey.
• Sites at Dingo Beach were comprised of fine to medium sandy sediments, were exposed to wave action and generally had a low seagrass abundance (<20% cover). At Dingo Beach wave action from prevailing south-easterly winds and strong tides results in sediment movement where fine muds are displaced with coarse sands and shell.
• There are no major rivers flowing into this coastal section and a high proportion of the catchment in this region is covered with native terrestrial vegetation. Negative impacts from catchment inputs and urban and agricultural development are likely to be low.
• The abundance of seagrass in the region represents a significant food source and valuable habitat for green sea turtle and dugong moving between Edgecombe Bay and the Whitsundays.

Hamilton Island

Principal watchers: Seagrass-Watch HQ
Location: Intertidal sand flats at either end of Catseye Bay
Site codes: HM1 & HM2
Issues: Sewage and groundwater
Comments: Turtle and fish feeding grounds

In mid 2007, Seagrass-Watch monitoring sites were established on Hamilton Is as part of the Great Barrier Reef Water Quality Protection Plan – Marine Monitoring Program.

Hamilton Island is the largest inhabited island of the Whitsunday Islands, a collection of wet drowned mountains situated close to the east coast of Queensland, Australia. The Whitsundays was named by Captain James Cook, who traveled through the area on Sunday 4 June 1770, which happened to be Whit Sunday (the seventh Sunday after Easter. The Whitsundays is a network of 74 islands of which 7 have resort facilities. Beyond the resorts the whole area is part of the Great Barrier Reef Marine Park and the uninhabited islands are all controlled by National Parks and Wildlife.

The most developed island is Hamilton Island, a major local and international tourist destination. Apart from the resort and village, much of the 750 hectares is still untouched. The island is also surrounded by fringing coral reefs, the largest in Catseye Bay in front of the main resort.

Nine seagrass species can be found in Catseye Bay: Halodule uninervis and Halophila ovalis are scattered over the sandy intertidal areas; patches of Zostera capricorni occur in the intertidal areas at the eastern end of the bay; Thalassia hemprichii, Cymodocea serrulata and Cymodocea rotundata are mixed in amongst the coral on the reef flat; Syringodium isoetifolium is present on the outer edge of the reef flat in the shallow subtidal waters; Halophila spinulosa occurs just over the edge of the reef crest in deeper waters (>3m); and on the shoreward edge of the coral area are small patches of rare Thalassodendron ciliatum (the southern most occurrence of this species in the Pacific).

The seagrasses in Catseye Bay are an important component of Hamilton Island’s marine ecosystem, providing shelter for fish and prawns and food for green sea turtles. In recent years there has been some concern about the co-existence of tourism and the environment, and the resort is doing it’s best to ensure impacts are minimised. For example, a couple of years ago an island resident expressed some concerns about jet-skis operating on the fringing reef close to where he had noticed turtles foraging daily. He witnessed one turtle get hit by a jet ski and several near misses. Although jet-ski’s and high speed motorised water sports are permitted in the Whitsunday Plan of Management, the resort operators repositioned the buoys marking the jet-ski circuit to increase their distance from the fringing reef where turtles forage most frequently.

The first detailed assessment of the Hamilton Island seagrass sites (HM1 and HM2) was conducted in late October 2007. Both sites are intertidal and located at either ends of Catseye Bay. HM1 is dominated by Halodule uninervis, with some Halophila ovalis, and located in front of the main resort within an area where motorised vessels are prohibited. This site is also the main feeding area frequented by green sea turtles. HM2 on the other hand is in the far east of the Bay and dominated by Zostera capricorni with Halodule uninervis and Halophila ovalis. This site has relatively no impacts from boating or resort activities.

It is hoped these sites will provide a critical component of the assessment of any long-term improvement in water quality that will occur as best land management practices are widely adopted across the Great Barrier Reef catchments and regions.

Hydeaway Bay

Principal watchers: Maren Mathews, Sunnee Goudy, Valda & Seagrass-Watch HQ
Occasional and past watchers: Dawn, Margaret Parr, Valerie Bunn & Wendy Galloway
Location: Large fringing reef-flat in north facing mainland bay, in the north of the region
Site codes: HB1 & HB2
Issues: Urban expansion, sewage and groundwater, siltation due to clearing and erosion
Comments: Turtle and fish feeding grounds

Status (Feb05):

• Hydeaway Bay meadows cover approximately 157ha and are predominately mixed meadows of Halodule uninervis, Halophila ovalis, Cymodocea rotundata and Thalassia hemprichii. The seagrass species composition has remained relatively stable over the monitoring period, indicative of natural and/or anthropogenic disturbance.
• Seagrass abundance follows a seasonal trend, characterised by maximum cover (>20% cover) in summer/autumn (December –April) and minimum cover (<20% cover) in winter (June-July). This suggests that seagrass meadows at these sites are primarily influenced by natural factors (temperature, light, wave action).
• At Hydeaway Bay maximum epiphyte cover (>35-75%) occurred in summer (December) and autumn (March), and minima in winter. Algal cover remained below 20% with no seasonal pattern. High epiphyte cover in spring-summer may have been caused by high water temperatures and light availability. High rainfall during summer may also enrich waters with nutrients necessary for epiphyte growth.
• The presence of large sea cucumbers present across the reef flat at both sites is a significant. The low numbers of gastropods, crabs and worms at Hydeaway Bay may be due to the different seagrass mix at these sites and a low supply of detrital matter in the coarse sandy sediments.
• Sites at Hydeaway Bay were comprised of fine to medium sandy sediments, exposed to wave action and generally had a low seagrass abundance (<20% cover). Hydeaway Bay sandy sediments had a low proportion of organic matter and seagrasses compete for space with corals (soft and hard) and macroalgae.
• There are no major rivers flowing into this coastal section and a high proportion of the catchment in this region is covered with native terrestrial vegetation. Negative impacts from catchment inputs and urban and agricultural development are likely to be low.
• The abundance of seagrass in the region represents a significant food source and valuable habitat for green sea turtle and dugong moving between Edgecombe Bay and the Whitsundays.

Laguna Quays

Principal watchers: Margaret Parr, Geoff Bunn & Seagrass-Watch HQ
Occasional and past watchers: Betty Wilson, John Thornely & Carolyn Williams
Location: sand/mud flat along western coast of Repulse Bay, 3km south of O'Connell River mouth
Site codes: MP1 & MP4
Issues: Resort and marina development, vessel traffic near dugong and turtle habitat, catchment inputs from agriculture, mangrove clearing
Comments: Dugong and turtle feeding grounds

Status (Feb05):

• Seagrass abundance at Laguna Quays followed a seasonal trend, characterised by maximum cover (>20% cover) in spring/summer (September –January) and minimum cover (<20% cover) in winter (June-July). This suggests that seagrass meadows at these sites were primarily influenced by natural factors (temperature, light, wave action).
• At Laguna Quays, MP1 was dominated by Halodule uninervis, and MP4 was dominated by Z. capricorni. The relative proportions of species at each site remained stable over the monitoring period.
• Low epiphyte cover (<30%) and algal cover (<1%) was recorded at Laguna Quays sites.
• Dugong feeding trails were abundant at Laguna Quays. The occurrence of feeding trails varied between sites but highest feeding activity was recorded in March and September 2000.
• The abundance of invertebrate fauna was less common at Laguna Quays compared to other locations in the region.
• Sites at Laguna Quays had fine to medium sandy sediments, were exposed to wave action and generally had a low abundance of seagrass (<20% cover) consisting of Halodule uninervis and Halophila ovalis.

Midge Point

Principal watchers: Paul Wenzler, Jennifer Wenzler, Tara Wenzler & Andrew Wenzler
Occasional and past watchers: Seagrass-Watch HQ
Location: sand/mud flat along coast of southern Repulse Bay
Site codes: MP2 & MP3
Issues: Low urban development, close to mangroves
Comments: Fish, dugong and turtle feeding grounds

Status (Feb05):

• Midge Point intertidal meadows cover approximately 30ha, which are predominately Zostera capricorni mixed with low amounts Halodule uninervis and Halophila ovalis. The relative proportions of species at each site remained stable over the monitoring period.
• Seagrass abundance at Midge Point followed a seasonal trend, characterised by maximum cover (>20% cover) in spring/summer (September –January) and minimum cover (<20% cover) in winter (June-July). This suggests that seagrass meadows at these sites were primarily influenced by natural factors (temperature, light, wave action).
• Low epiphyte cover (<30%) and algal cover (<1%) was recorded at Midge Point sites.
• Dugong feeding trails were abundant at Midge Point.
• Gastropods and hermit crabs were common at Midge Point where high seagrass abundance provided a supply of detritus, grazing matter and faunal prey.
• Tidal dominated localities at Midge Point were composed of fine mud and sand sediments with a high organic component. Disturbance to seagrass meadows may be caused by a number of factors. At Midge Point wave action from prevailing south-easterly winds and strong tides resulted in sediment movement where fine muds were displaced with coarse sands and shell.

Midgeton

Principal watchers: Margaret Parr, Dell Williams Graeme Hyde, Seagrass-Watch HQ
Occasional and past watchers: Betty Wilson, John Williams, Heather Hyde & Valerie Bunn
Location: Near mouth of Dempster Creek estuary south of Midge Point
Site codes: MT1 & MT2
Issues: Native vegetation adjacent Exposed sand/mud flat
Comments: Dugong, turtle and fish feeding grounds

Status (Feb05):

• Seagrass abundance at Midgeton followed a seasonal trend, characterised by maximum cover (>20% cover) in spring/summer (September –January) and minimum cover (<20% cover) in winter (June-July). This suggests that seagrass meadows at these sites are primarily influenced by natural factors (temperature, light, wave action). In 2000 and 2003 the opposite trend occurred at Midgeton with a decline in seagrass cover from July (winter) to February (summer). Midgeton is located at the mouth of Dempster Creek and this decline in seagrass cover was possibly due to disturbance from sediment movement associated with rainfall and freshwater inputs, together with strong wave action and south easterly winds.
• Sites at Midgeton consist of an equal mix of Z.capricorni, H. uninervis and H. ovalis. The relative proportions of species at each site remained stable over the monitoring period.
• Epiphyte cover (40-70%) at Midgeton sites was high in spring-summer (December) and low in winter (June). Algal cover remained low (<2%) at these sites.
• Dugong feeding trails are abundant at Midgeton. The occurrence of feeding trails varied between sites but highest feeding activity was recorded in March and September 2000.
• The abundance of invertebrate fauna was less common compared to other locations in the region.
• Tidal dominated localities at Midgeton were composed of fine mud and sand sediments with a high organic component. At Midgeton sites freshwater flows from the Dempster Creek may also contribute to sediment disturbance.

Pigeon Island (Pioneer Bay)

Principal watchers: Margaret Parr, Amanda Parr, Geoff Bunn, Robin Salmon, Valerie Bunn, Sandra Hardy, Betty Wilson, Dell Williams, Eileen Lewis, Helen Debnam, Jacquie Shiels, John Schmidt, John Williams, Alderd Lenting, Eileen Lavis & Seagrass-Watch HQ
Occasional and past watchers: Aileen Gleeson, Blair Wilson, Carolyn Williams, Fran Guard, Joanne, Judy Chapman & Lise Schimdt
Location: Intertidal sand/mud flats adjacent to Cannovale township in southern Pioneer Bay
Site codes: PI1, PI2, PI3, PI4
Issues: High marina & urban development, adjacent to sewage treatment outfall
Comments: Dugong and turtle feeding grounds

Status (Feb05):

• Intertidal meadows in Pioneer Bay in the vicinity of Pigeon Island cover approximately 60ha, which are predominately Halodule uninervis and Halophila ovalis mixed with low amounts Zostera capricorni.
• Seagrass abundance followed a seasonal trend, characterised by maximum cover (>20% cover) in summer/autumn (December –April) and minimum cover (<20% cover) in winter (June-July). This suggests that seagrass meadows at these sites are primarily influenced by natural factors (temperature, light, wave action). At two sites (PI1 and PI2) seagrass cover was relatively high, a possible consequence of elevated nutrients from an adjacent sewage outfall. Seagrass at the other sites (PI3 and PI4) however, were highly variable and remained low (<15%).
• At most Pigeon Island sites the composition of Halodule uninervis and Halophila ovalis remained relatively stable over the monitoring period, their dominance indicative of natural and/or anthropogenic disturbance. At PI1 Zostera capricorni increased in dominance throughout the monitoring period, suggesting that this site is subject to less disturbance than other sites in the area.
• Epiphyte cover on seagrass leaves at Pigeon Island was high (30-70%) and persisted throughout much of the year. Algal cover was high (10-50%) in winter (June), spring (September) and summer (December). High algal growth at Pigeon Island indicates nutrient enrichment from local sources (ie marina development, sewage outfall, stormwater runoff) and impact on seagrass meadows.
• Dugong feeding trails were abundant at Pigeon Island sites. The occurrence of feeding trails varied between sites but highest feeding activity was recorded in March and September.
• Gastropods and hermit crabs were abundant at Pigeon Island. The high abundance of invertebrate fauna at these sites suggested that seagrass provides an adequate supply of detritus, grazing matter and faunal prey. An exception was site PI4 where low numbers of gastropods and crabs suggest an impacted seagrass habitat.
• Anthropogenic disturbance (sewage inputs, stormwater runoff, boat discharges) at Pigeon Island results in accumulation of fine muds with a high organic component. In 2003, the accumulation of fine mud across the monitoring sites was of some concern (see newsletter 17, June 2003), however the mud levels in the sediment composition appear to be abating.

Whitehaven Beach

Principal watchers: Tony Fontes & Amanda Parr
Occasional and past watchers: Chris Chandler, Glenn Carvath & Sean Andrew
Location: Subtidal shores of beach on the eastern coast of Whitsunday Island
Site codes: WB1, WB2, WB3
Issues: High boat usage, anchoring
Comments: Turtle and fish feeding grounds

Status (Feb05):

• Subtidal meadows at Whitehaven Beach cover approximately 365ha, which are predominately a mix of Halodule uninervis, Halophila ovalis, Cymodocea serrulata and Syringodium isoetifolium.
• Sites were established in relation to anchoring impacts - high impact site (WB3) and low impact site (WB2). Species composition at WB3 (high impact site) contained a higher proportion of H. ovalis and S. isotetifolium than at the low impact site (WB2). Both species colonise disturbed areas and were in highest abundance from spring to summer when light and temperature are favourable for fast growth.
• From 1987 to 1999-2000 seagrass meadows at Whitehaven Beach increased in area, with the seaward edge extending up to 300m beyond the edge mapped in 1987.
• Seagrass abundance is characterised by maximum cover in spring/summer (September – December) and minimum cover (<15%) in winter (June-July). At initiation of monitoring, seagrass cover was significantly higher at the low anchor use site (WB2) compared with high anchor use site (WB3), suggesting that boat anchors cause a reduction in seagrass abundance. These areas are subject to few disturbances compared with sites situated near heavy tourism. A study was conducted to identify the type of damage to seagrass caused by anchor chains and anchors from boats of different size classes (see Campbell and McKenzie 2001). The findings suggest that larger boats cause greater damage to seagrass than small boats because of longer anchor chains and the thickness of chain used. The use of plough anchors in preference to sand anchors may also contribute to increased seagrass damage, because of the high probability of anchor and chain movement causing deep anchor scars and long chain scars. Since late 2001, seagrass abundance has shown a steady decline at both the impacted and unimpacted sites – in fact, the unimpacted site is no longer significantly better.
• Abundance of epiphytic and non-attached algae at WB2 and WB3 was generally low (<10%) for most of the monitoring period. In autumn (March 2001) the blue green alga Lyngbya majuscula covered extensive areas (35-70%) of seagrass. Lyngbya majuscula is a toxic filamentous cyanobacterium found in tropical and sub-tropical marine and estuarine environments worldwide. This cyanobacterium is commonly called "mermaids hair" or "fireweed". In bloom conditions Lyngbya forms dense mats that cover the sea floor, smothering underlying seagrass meadows. The cause of the bloom is unknown, but may be associated with favourable light and temperature conditions, and/or a local source of nutrients from nearby freshwater inputs and boat discharges.
• Epi-fauna on seagrass blades at Whitehaven Beach sites were less abundant than other subtidal sites in the region, suggestive of disturbance from boat anchors and chains.
• Evidence of dugong and turtle grazing was low at Whitehaven Beach.
• Sediments at Whitehaven Beach sites were composed of fine mud, sand and shell with a high organic component. Disturbance at Whitehaven Beach sites from boat anchors was high and resulted in decreased seagrass cover and epi-faunal abundance. Anchor damage and algal overgrowth were the primary causes of seagrass damage in these areas.