They suggest that high nutrient levels can significantly alter marsh processes and increase gross carbon loss from sediment but that other processes may compensate for these impacts. No net deleterious effects of nutrient loading on carbon storage or on marsh stability are anticipated from this study (Anisfeld and Hill 2012). Other eutrophication studies performed in Narragansett Bay, Rhode Island found that experimental nitrogen addition initially increases plant productivity but eventually leads to reduced plant biomass due to insect herbivory (Bertness et al. 2008). To supplement this experiment, researchers took surveys across 20 salt marshes to look at the interaction between marsh nutrient levels and herbivore pressure and found that marsh nitrogen supply was a good predictor of herbivore damage to plants. This study suggests that eutrophication is currently triggering consumer suppression of primary productivity in New England salt marshes and may eventually pose a threat to salt marsh ecosystem service provisioning (Bertness et al. 2008). Coastal ecosystems suffer from a variety of anthropogenic impacts, such as large-scale eutrophication, food web alteration, runaway consumer effects, climate change, habitat destruction, and disease. Rarely do these factors act in isolated ways. Often, researchers find additive or synergistic interactions between impacts compounding the amount of ecosystem degradation. One such example is found in salt marshes in the southeastern United States. Depletion of top predators in these systems has led to snail overgrazing of salt marsh cordgrass and subsequent die-off (as explained above). However, this die-off has been linked with intense drought conditions and the resultant increases in salt and acid stress (Silliman et al. 2005). Drought stress that raises soil salinities and increases cordgrass vulnerabilities to top-down control may be a product of climate change (Silliman and Bertness 2002, Silliman et al. 2005). Cases such as these highlight how abiotic and biotic interactions can interact to affect ecosystem health. Anthropogenic actions also can cause eutrophication, or increase the nutrient load, of marine ecosystems, through runoff into the system containing fertilizer, sewage, dishwasher soap, and other nitrogen- and phosphorus-rich substances. Eutrophication is pervasive in coastal marine ecosystems (Lotze et al. 2006) and can indirectly initiate trophic cascades and increase consumer control of plants. For example, insect herbivory in marshes has been positively correlated with nutrient availability in Atlantic salt marshes (Bertness et al. 2008).