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Riparian Monitoring on Santa Rosa Island, California: A Survey of Water Quality and Benthic Macroinvertebrates
The health of riparian ecosystems on Santa Rosa Island has been closely monitored since the removal of grazing ungulates in 1998, in addition to other restoration efforts. In a study by the National Park Service published in 2004, monitoring revealed a distinct improvement from a previous study published in 1998 (with data collected in 1992-97 before the removal of cattle) (Rosenlieb et al. 1995; NPS 2004). Comparisons are also made to chemical water quality data and a survey of benthic macroinvertebrates (BMI’s) collected in 2005-2007 and published in a UC Santa Barbara report (Melack and Cooper 2008). We collected data on several chemical parameters and BMI’s across five watersheds on northern Santa Rosa Island. We analyzed the data collected in this study to both assess changes in water quality since the previous studies, and to test the efficacy of the sampling locations in the previous 2002 study to represent the entire island. We conclude based on chemical data that the health of the riparian ecosystem has continued to improve, albeit at different paces in different watersheds. Some parameters like pH remain relatively unchanged while others such as nitrate and ammonium show surprising increases. We also found that the study locations in the 2002 monitoring period were adequate representations of overall water quality. Although BMI communities mainly consisted of a moderately disturbance tolerant crustacean (Hyalella azteca) and the mayfly family Baetidae, benthic macroinvertebrate sampling indicated improved stream health since 2008 in Lobo, Quemada and Water Canyons.
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