The island, also known by its aboriginal name of Minjerribah, is surrounded by extensive seagrass meadows which are grazed by fishes, turtles, and dugongs and serve as nursery grounds for other native species. The unusual geomorphology of NSI allows rainwater to recharge a massive aquifer of groundwater, forming a “central mound” or lens of freshwater under the island. Pressure within this aquifer prevents saltwater intrusion and drives groundwater out beyond the coastline and into numerous creeks, swamps, window lakes, and springs on the island. One such release point is Myora Springs, located on the west coastline of NSI. Myora springs discharges approximately 2.4 million liters day21 of groundwater through a mangrove AP24534 forest and paperbark swamp and into Moreton Bay. Here spring waters mix with seawater over shallow seagrass meadows dominated by eelgrass, Zostera muelleri. The degree of mixing is dependent upon the tides; for at least several hours per tidal cycle, at low tide, the effluent extends over 2500 m2 of exposed seagrass meadow. Several observations suggested that spring effluent might be impacting the shallow water marine community at this site; for example, anecdotal reports from local fisherman describe pitted and eroded shells in this area and we observed a lack of calcareous epiphytes on seagrasses near the shoreline, both of which suggest possible low pH conditions. Indeed, a preliminary study in January 2012 revealed that spring effluent, pH 5, extended over exposed seagrass meadows during low tides, depressing seawater pH by,0.5 units at a distance of 10–20 m from the edge of the mangrove forest, without detectable changes in salinity at this distance. Previously we found that low pH conditions and the corresponding increases in seawater CO2 levels were associated with a dramatic loss of protective phenolic substances, including phenolic acids and condensed tannins, in four different populations of seagrass. These results were surprising since terrestrial plants exposed to elevated CO2 conditions often exhibit increased levels of many ‘carbon-based’ secondary metabolites, including phenolics. Indeed, light and carbon availability stimulate the shikimic acid and phenylpropenoid pathways that synthesize most plant phenolics. Whatever the cause, such a loss of seagrass phenolics may have ecological consequences; they serve as herbivore deterrents, digestion reducers, and antifoulants and some possess antimicrobial properties, inhibiting the growth of the marine pathogen Labyrinthula which causes the seagrass wasting disease. In the earlier set of experiments the potential impacts on herbivores were not investigated because there were few important seagrass grazers at those study sites. In contrast, there are numerous large herbivores consuming significant quantities of seagrass in Moreton Bay. Most other conditions were unaffected, or affected to a minimal degree. Eelgrass shoots collected near the outflow of the spring were apparently healthy and, except for a lack of calcareous epiphytes, indistinguishable from plants collected 30–50 meters away. Seagrass proximity to the spring altered the feeding behavior of a native grazer, the black rabbitfish, Siganus fuscescens.