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 were exposed to 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 in(p<0.05) in jellyfish growth at all concentrations and at levels0.1 µg.L-1, a level that is below the regional Great Barrier Reef guideline valuesvalue. 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

Investigating the potential of jellyfishes as marine biomonitors and bioindicators of metal pollution

Metal pollution has long been recognised as having a significant impact on the biodiversity and health of marine coastal systems. The use of biomonitor and bioindicator species is widely accepted for protecting ecosystem integrity and remediation of impacted systems. Species used as biomonitors in marine systems are typically benthic sessile species with a tolerance to the pollutant under investigation. In contrast, bioindicator species need to be sensitive to the pollutant. Historically, jellyfishes have not been regarded as useful bioindicators as they have been considered very tolerant of polluted environments and thus not evaluated in the suite of indicator species. Their pelagic behaviour and seasonality also mean they have not previously been considered useful biomonitor species despite their potentially high seasonal abundance in coastal systems. Notwithstanding these factors, current concerns about increased jellyfish blooms and their ability to cycle large quantities of inorganic elements suggest jellyfishes could fulfil a useful role in assessing ecosystem health.\ud \ud The objective of this project was to assess the potential jellyfishes have as biomonitors or bioindicators to the effects of dissolved metals. The research focused on the response of scyphozoan and cubozoan jellyfishes to metal exposure and assessed bioaccumulative capacity and retention as well as sensitivity to metals. To assess the biomonitoring capacity, elemental concentrations in tissues of jellyfishes were measured at multiple locations on the Great Barrier Reef over a three year period. Scyphozoan jellyfishes accumulated higher concentrations of elements at coastal and inshore locations compared with off-shore locations, which likely reflected the gradient of terrestrially derived elements into the marine system. Symbiotic scyphozoan jellyfishes typically had higher body concentrations of elements than their asymbiotic relatives collected from the same location and time. Further, variations in elemental tissue concentrations among cubozoan jellyfishes were species dependent.\ud \ud Laboratory assessment of the bioconcentration of aqueous copper or zinc in the symbiotic rhizostome jellyfish Cassiopea sp. showed that both metals readily accumulated in tissues at levels that were orders of magnitude above ambient water concentrations. However, the accumulative capacity and retention time varied between the metals. Copper was accumulated more rapidly and excreted more rapidly post-exposure (biological half-life 1.7 days), while zinc was accumulated more slowly and did not reach saturation during the study but was retained for much longer (biological half-life 9.1 days). Although the exact mechanisms of uptake and retention were not identified, it was apparent that accumulation and retention strategies in Cassiopea sp. were strongly metal dependent.\ud \ud To assess the bioindicator potential of jellyfishes, a series of laboratory studies measured the acute effects of copper and zinc at multiple lifestages in three species of jellyfish. From the outcomes of the acute toxicity, additional studies were conducted using the most sensitive species to determine sub-lethal responses of the jellyfish to copper or zinc exposure.\ud \ud The acute toxicity of aqueous copper and zinc was assessed in three species of jellyfish representing symbiotic (Cassiopea sp.) and asymbiotic Scyphozoa (Aurelia sp.), and a cubozoan jellyfish (Alatina mordens). Copper was an order of magnitude more toxic to all species and lifestages than zinc. Cassiopea sp. was more sensitive to both copper and zinc exposure than Alatina mordens. Aurelia sp. was the least sensitive of the three species to both metals. Sensitivity to copper and zinc varied among lifestage also, with the newly metamorphosed / strobilated stages being more sensitive than the benthic polyps in the three species.\ud \ud Cassiopea sp. was the most sensitive species from the acute toxicity studies. Sub-lethal toxicity to copper and zinc was assessed for both the jellyfish and its endosymbiont zooxanthellae. The response of the zooxanthellae was tested using photosynthetic yield as the end point and the host jellyfish response was assessed using change in bell diameter. There was a decrease in photosynthetic yield in the zooxanthellae exposed to increasing concentrations of copper or zinc although this was only significant at the higher concentrations (24 μg.L⁻¹ Cu, 0.88 mg.L⁻¹ Zn). Post-experiment counts of zooxanthellae abundances showed that the jellyfish did not expel the symbionts as a stress response to metal exposure, so that the change in photosynthetic yield resulted from decreased zooxanthellae activity rather than decreased abundance in the host tissues. Change in bell diameter of the Cassiopea sp. was significant at all concentrations of copper and zinc tested. This demonstrated that the host response was the more sensitive measure of exposure to copper or zinc than symbiont activity.\ud \ud In conclusion, the project demonstrated that jellyfishes were sensitive to metal pollution and have potential as bioindicators. The responses were variable among species and lifestages but demonstrated high sensitivity comparable to other marine bioindicators (e.g. hermatypic corals and molluscs). When exposed to low concentrations of metals, jellyfishes were capable of concentrating metals in their tissues and retaining them for days to weeks suggesting they are of high utility as marine biomonitors. These outcomes challenge historical views that jellyfish are more tolerant to pollutants than most marine taxa and are more likely to persist under poor environmental conditions. It also demonstrates that jellyfishes have strong potential for monitoring and assessing ecosystem health

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

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

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

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 24 h 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

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 were exposed to 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 in(p<0.05) in jellyfish growth at all concentrations and at levels0.1 µg.L-1, a level that is below the regional Great Barrier Reef guideline valuesvalue. 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

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

Multiple Verdazyl Radicals Appended to a Triarylamine Scaffold

We report the synthesis of three triphenylamine-based verdazyl radicals. These include a mono, bis, and tris(verdazyl) at the 4-position(s) of the N–Ar groups, containing one, two, and three unpaired electrons, respectively. Each of these compounds is air stable, and fully characterized using EPR spectroscopy, high-resolution mass spectrometry, infrared spectroscopy, UV/Vis spectroscopy, and cyclic voltammetry. From the UV/Vis absorbance data, the optical absorbance energy gaps were found to be ~2.35 eV for all three verdazyl-containing compounds. Cyclic voltammetry was used to estimate the energy levels of the singly occupied molecular orbitals (SOMOs), which are -4.91 eV, -5.12 eV, and -4.98 eV for mono, bis, and tris(verdazyl) compounds respectively. Spin-spin exchange interactions were observed in the EPR spectra of both the bis and tris(verdazyl)s, leading to additional hyperfine coupling patterns and assignment of the ground states as triplet and quartet, respectively

The Behavioural Impact on Cats during a Transition from a Clay-Based Litter to a Plant-Based Litter

Current guidelines recommend transitioning cats from one litter product to another over 6 days to minimize stress. The study objective was therefore to test these guidelines using 16 adult domestic cats (2 cohorts of 8) by observing behavioural changes associated with elimination throughout the litter transition. Cats were transitioned from a clay-based litter (CLAY) to a plant-based litter product (PLANT) over 6 days (period 1) via an incremental replacement of CLAY with PLANT. All cats then remained on PLANT for 8 days (period 2). This same transition process was executed for both cohorts, and litter box behaviours were observed via remote recording. Urination, defecation, cover, and dig behaviours were not different between periods 1 and 2 (p > 0.05). Sniffing frequency was greater in period 2 than period 1 (p p < 0.05). These data suggest that 6 days may be an adequate amount of time to transition a cat to a new litter, although successful transition may also be specific to the types of litters investigated