The utility of jellyfish as marine biomonitors.

Jellyfish are abundant in coastal waters across broad latitudinal ranges and are often considered pests and a group that can cause phase shifts in marine ecosystems. Recent studies have highlighted their potential as biomonitors of contaminants including metals, herbicides and nutrients. Traditionally, sedentary organisms like molluscs and annelid worms have been used, but some jellyfish have similar characteristics of localised distributions and in some cases sedentary behaviour. Broad gradients in contaminant accumulation have been shown for a number of planktonic jellyfish species. An alternative biomonitoring candidate is the tropical/sub-tropical upside-down jellyfish (Cassiopea spp.). In laboratory and field deployments, Cassiopea accumulate measurable contaminants over days to weeks, making them ideal for detecting short-term pulses. Furthermore, the decay curve of contaminants varies temporally post-exposure and contaminant type. This can provide an estimate of the timing of exposure. Cassiopea, along with other jellyfish, have the potential to be an interesting and valuable group of organisms for monitoring coastal impacts.

Detecting effects of herbicide runoff: The use of Cassiopea maremetens as a biomonitor to hexazinone.

Herbicides are an integral part of global agricultural activity but can be advected into local drainages that can discharge to coastal marine systems. Herbicide runoff can impact coastal marine organisms, including those associated with coral reefs and coastal mangrove forests. In this study, the symbiotic sedentary jellyfish Cassiopea maremetens were exposed to analytical grade hexazinone to determine their sensitivity and potential for recovery after exposure to a press herbicide event of 14 days followed by a recovery period of matching duration. Bell surface area, photosynthetic yield (i.e. effective quantum yield, EQY), statolith count and zooxanthellae density were analyzed. Most metrics demonstrated significant decreases when exposed to higher concentrations of hexazinone, while EQY was significantly decreased at exposure concentrations from 31 µg/L hexazinone and above. In contrast, zooxanthellae density (cells/mm2) increased in the highest concentrations compared to control animals. At the end of the exposure period the EC50 for bell surface area, EQY, and statolith count were 176 µg/L, 81.96 µg/L, and 304.3 µg/L, respectively. Jellyfish were able to recover to similar start values for all measured metrics at the end of the 14-day recovery period, with EQY showing recovery by Day 7 of the recovery period. This study demonstrated that statolith counts as an estimate of age were not affected by herbicides. We conclude that the depressed metrics from herbicide related impacts of C. maremetens are effective indicators of a relatively recent herbicide perturbation in that the recovery timeframe for these jellyfish is relatively short.

Herbicide effects on the growth and photosynthetic efficiency of Cassiopea maremetens.

Herbicides from agricultural run-off have been measured in coastal systems of the Great Barrier Reef over many years. Non-target herbicide exposure, especially photosystem II herbicides has the potential to affect seagrasses and other marine species. The symbiotic benthic jellyfish Cassiopea maremetens is present in tropical/sub-tropical estuarine and marine environments. Jellyfish (n = 8 per treatment) were exposed to four separate concentrations of agricultural formulations of diuron or hexazinone to determine their sensitivity and potential for recovery to pulsed herbicide exposure. Jellyfish growth, symbiont photosynthetic activity and zooxanthellae density were analysed for herbicide-induced changes for 7 days followed by a 7 day recovery period. Both the jellyfish and endosymbiont were more sensitive to diuron than hexazinone. The 7-day EC50 for jellyfish growth was 0.35 µg L-1 for Diuron and 17.5 µg L-1 for Hexazinone respectively. Diuron exposure caused a significant decrease (p < 0.05) in jellyfish growth at 0.1 µg L-1, a level that is below the regional Great Barrier Reef guideline value. Jellyfish recovery was rapid with growth rates similar to control animals following removal from herbicide exposure. Both diuron and hexazinone caused significant decreases in photosynthetic efficiency (effective quantum yield) in all treatment concentrations (0.1 µg L-1 and above) and this effect continued in the post-exposure period. As this species is frequently found in near-shore environments, they may be particularly vulnerable to herbicide run-off.

Fine-scale detection of pollutants by a benthic marine jellyfish.

Local sources of pollution can vary immensely on small geographic scales and short time frames due to differences in runoff and adjacent land use. This study examined the rate of uptake and retention of trace metals in Cassiopea maremetens, a benthic marine jellyfish, over a short time frame and in the presence of multiple pollutants. This study also validated the ability of C. maremetens to uptake metals in the field. Experimental manipulation demonstrated that metal accumulation in jellyfish tissue began within 24h of exposure to treated water and trended for higher accumulation in the presence of multiple pollutants. C. maremetens was found to uptake trace metals in the field and provide unique signatures among locations. This fine-scale detection and rapid accumulation of metals in jellyfish tissue can have major implications for both biomonitoring and the trophic transfer of pollutants through local ecosystems.

Predicting aqueous copper and zinc accumulation in the upside-down jellyfish Cassiopea maremetens through the use of biokinetic models.

Jellyfish have a demonstrated capability to accumulate metals within their tissues, but to date, there have been no quantitative assessments of accumulation and retention rates and patterns. Bioconcentration patterns of copper and zinc in the upside-down jellyfish Cassiopea maremetens were modelled over a 28-day study (14 days exposure followed by 14 days clearance). C. maremetens accumulated copper over 14 days with the maximum calculated copper concentrations at 33.78 µg g(-1) dry weight and bioconcentrated to 99 times water concentrations. Zinc was also accumulated during the exposure period and retained for longer. The maximum theoretical zinc concentration was 125.1 µg g(-1) dry weight with a kinetic bioconcentration factor of 104. The patterns of uptake and retention were different between the elements. The use of kinetic models provided adequate predictions of aqueous metal uptake and retention in C. maremetens. This species has the capacity to very rapidly absorb measurable metals from short-term water-metal exposure.

Trace element accumulation in Cassiopea sp. (Scyphozoa) from urban marine environments in Australia.

Jellyfishes are robust, short-lived animals, tolerant to a wide range of environmental conditions and pollutants. The benthic jellyfish, Cassiopea sp. was collected from five locations along the north and eastern coast of Australia and analysed for trace elements to determine if this species has potential as a marine biomonitor. Both the oral arm and bell tissues readily accumulated aluminium, arsenic, barium, cadmium, chromium, copper, iron, manganese and zinc above ambient seawater levels. In contrast, lithium appeared to be actively regulated within the tissues while calcium, magnesium and strontium reflected the ambient environment. The multi-element signatures showed spatial variation, reflecting the geographical separations between locations, with locations closer together showing more similar elemental patterns. The combination of bioaccumulative capacity, life history traits and biophysical aspects indicate that this species has high potential as a biomonitor in coastal marine systems.