Summary and Findings
Monterey Bay National Marine Sanctuary

Monterey Bay National Marine Sanctuary is a federal marine protected area encompassing over 6,000 square miles in the United States. Within the boundaries of the sanctuary is a rich array of habitats, from rugged rocky shores and lush kelp forests to an underwater mountain, and one of the largest underwater canyons in North America. These habitats abound with life, from tiny microscopic plants to enormous blue whales. The sanctuary is home to a diversity of species including marine mammals, seabirds and shorebirds, sea turtles, fishes, invertebrates and marine algae.

The purpose of a condition report is to use the best available science and most recent data to assess the status of various parts of the sanctuary’s ecosystem. Because of the considerable differences within the sanctuary between the estuarine, nearshore, offshore and seamount environments (Figure 1), each question found in the State of the Sanctuary Resources section of this report was answered separately for each environment. Though many estuaries occur along the central California coastline, they are not within the sanctuary’s boundaries. Elkhorn Slough is the only estuary located inside MBNMS’s boundaries, and thus, is the focus of the estuarine environment section in this report. The nearshore environment is defined as extending from the shoreline boundary of the sanctuary (mean high water) to the 30 meter isobaths, and includes the seafloor and water column. The offshore environment is defined as extending from the 30 meter isobath out to the offshore boundary of the sanctuary, and includes the seafloor and water column. The seamount environment includes the seamount and surrounding seafloor and water column within the Davidson Seamount Management Zone (DSMZ). The DSMZ was added to MBNMS in November 2008 and has been assessed for the first time in this update.

The 2015 assessment of the estuarine environment of Elkhorn Slough reinforces our 2009 assessment that this is an area of concern within the sanctuary. Elkhorn Slough has a history of extensive alteration of physical structures and natural processes that strongly impacts water quality, habitat quality and abundance, and the structure and health of the faunal assemblage. Continued inputs of nutrients and contaminants, especially in areas of muted tidal influence, are contributing to events, such as frequent hypoxia, algal blooms and impacts to sensitive species. Historic human modifications to this system have led to substantial changes in hydrology, erosion and sedimentation that continue to impact the abundance and quality of habitats and living resources. There is a high percentage of non-native species competing with native species and impacting ecosystem health. Some key species, such as eelgrass, native oysters and sea otters, are showing signs of improvement. The slough is the focus of new and on-going conservation and restoration efforts. In the coming years, restoration projects and improvements in land management practices should result in some measurable improvements in water and habitat quality in portions of the slough.

The nearshore environment, which includes the shoreline out to 30 meters depth, is the main zone of interaction between humans and the sanctuary. This is the zone where most residents and visitors interact with sanctuary resources, and where most human activities have the strongest influence. As such, this environment receives a lot of research and resource management attention. Habitats in less impacted areas are in good condition (e.g., Big Sur), but there are concerns about localized on-going activities, including sand mining, coastal armoring, inputs of contaminants and marine debris. A high percentage of the sanctuary’s beaches regularly monitored for safety of swimming, received good grades in the last five years, likely due to improvements in sanitary sewer infrastructure in coastal cities. The nearshore waters continue to receive nutrient enrichments from land-based activity, which can intensify the effects of harmful algal blooms (HABs) on sensitive species. Decreases in persistent organic pollutants (dieldrin, dichlorodiphenyltrichloroethane [DDT], polybrominated diphenyl ethers [PBDEs]) were observed in mussels at five locations, but there is limited information available on new pollutants, such as current-use pesticides and pharmaceuticals. Recent drastic declines in sea stars, a key species in nearshore habitats, are a concern, but potential impacts on ecological function and biodiversity will take time to understand.

In the offshore environment, which extends from 30 meters depth to the seaward boundary, most of the regularly monitored key species and species assemblages appear to be stable. Pollutants (e.g., polychlorinated biphenyls [PCBs]), marine debris and toxins from Harmful Algal Blooms (HABs) were detected in some key species. There are concerns about impacts to sensitive species from human-caused noise, vessel traffic and entanglement in lines from buoys, and lost and active fishing gear. Bottom trawl fishing has decreased in intensity and spatial extent, as well as changed to less damaging gear and moved to less sensitive habitats. Recovery of formerly impacted habitats and structure-forming species is expected. The recent prevalence of unusually warm water along the U.S. West Coast has altered the distribution and abundance of some temperature-sensitive species and led to stranding events for a couple key species; however, more time is needed to determine if this phenomenon will have any persistent impacts on key species or the structure and function of the offshore ecosystem. Impacts from climate change, including acidification, warming and shoaling of the oxygen minimum zone, are starting to be detected, but much more research and monitoring is required to better understand and predict current and future impacts.

This first assessment of the seamount environment found benthic habitats and living resources on or near Davidson Seamount appear to be in good condition. Due to its depth, distance from shore and regulatory protections, the seamount area has not been impacted by human activities to the extent of other sanctuary offshore areas. Corals, sponges and other benthic fauna appear to be in pristine or near-pristine condition. Some threats exist, such as vessel traffic and changes in climate change, especially ocean acidification. More research and monitoring of water quality, habitat and living-resources associated with the seamount are needed to better understand the current status and predict potential impacts of human activities and changing climate.

Overall, this updated assessment of the state of sanctuary resources indicates that the sanctuary is doing quite well in comparison to other parts of the world’s ocean. The abundance and diversity of wildlife seen in Monterey Bay is remarkable compared to many parts of the world, and many sanctuary resources are showing relative stability or improvement. Long-term monitoring along rocky shores and in kelp forests shows that biogenic habitat, including canopy-forming kelp, understory algae and many structure-forming invertebrates, have been generally abundant and stable. The number of native species in sanctuary habitats, one measure of biodiversity, appears to be stable with no known losses of native species. Though some non-native species are present in the sanctuary, no new introductions are known to have occurred in any of the sanctuary’s environments.  Most of the sanctuary’s regularly monitored key species and species assemblages appear to be stable or slightly improving in status.

Nonetheless, a main purpose of this condition assessment is to identify problems with sanctuary health, so that management can focus on finding opportunities to improve conditions. We have identified some localized problems and some declining trends. Pressures on sanctuary resources are diverse. Some of the most prominent pressures include marine debris, vessel traffic, commercial and recreational fishing, agricultural and urban runoff, harmful algal blooms, coastal development and disturbances to wildlife. In addition, larger, more global issues, such as climate change and ocean acidification, are significant areas of concern, where some impacts are being detected, but long-term effects are not well understood.