Second Kona Integrated Ecosystem Assessment Survey Completed

The Kona Integrated Ecosystem Assessment (IEA) project aims to develop a comprehensive understanding of the ecosystem in the Kona coastal region of the island of Hawaii. As part of the research agenda supporting the Kona IEA project, PIFSC scientists have planned a series of shipboard biological and oceanographic surveys along the Kona Coast. The inaugural survey was conducted in 2011. The second Kona IEA survey was completed in mid-June 2013 aboard the NOAA Ship Oscar Elton Sette and involved scientists from PIFSC, the University of Hawaii's Joint Institute for Marine and Atmospheric Research, the University of Hawaii at Manoa and Hilo, NOAA's Hawaiian Islands Humpback Whale National Marine Sanctuary, and Duke University. And, in keeping with the goal of supporting students and educators, eight graduate and two undergraduate students and a NOAA Teacher at Sea participated in the survey.

Six research stations off Kona and seven transects between these stations were sampled. As in 2011, sampling operations included active acoustics, mid-water net trawls, and conductivity-temperature-depth (CTD) casts. Active acoustics are used to determine the depth and density of high sonic scattering layers, which are composed of small fish, squid, and crustaceans that larger species prey upon. Nightly mid-water trawls targeted the sonic scattering layer. Analysis of the trawl catch will provide information useful in interpreting the active acoustic data and understanding population connectivity. CTD casts gather data on temperature, salinity, dissolved oxygen, and chlorophyll concentration in the water column, providing details on Kona's physical environment and on the abundance and composition of the phytoplankton community which provides energy to all higher trophic level species.

In addition to replicating some aspects of the 2011 survey, this year's survey also gathered information to create cetacean habitat models for the Kona region. This included both visual and passive acoustic observations of cetaceans to determine their habitat areas, as well as the active acoustic and oceanographic sampling mentioned above to determine key characteristics of the habitat. The trawl catch details will also be used to help further our understanding of cetaceans' forage. Additionally, a University of Hawaii imaging sonar was deployed through sonic scattering layers to gather high-resolution data on the density of these layers, which will provide further information on the cetaceans' forage base and help with interpretation of the active acoustic data.

Data collected on this year's Kona IEA survey give a comprehensive snapshot of the Kona coast ecosystem, from the physical environment to the base of the marine food web to top predators. While the synthesis of these data is only beginning, a few insights are already apparent. The left-hand figure below shows temperature and chlorophyll transects in the survey area. These indicate that there is a shoaling and intensification of the deep chlorophyll maximum at both the offshore and inshore northern stations compared to the southern and central stations. Further, cetacean vocalizations, indicated by dots in the right-hand figure, are most abundant inshore and along the southern transect. Combining information gathered on this year's survey with data from 2011 will provide further insight into important features of Kona's ecosystem. We expect to conduct the next Kona IEA survey in the summer of 2015.

Left: Offshore and nearshore temperature and chlorophyll profiles derived from CTD casts conducted at each of the six Kona IEA 
               stations. 
               Right: Trawl catch composition, with circles scaled by catch volume.  Volumes are the average of two nightly tows, with the 
               exception of the east-central and northwest stations, where one nightly tow at each site was compromised by cookie cutter shark 
               bites to the trawl's cod end.  Black dots show locations of cetacean vocalizations.  The dashed lines indicate transects.
Left: Offshore and nearshore temperature and chlorophyll profiles derived from CTD casts conducted at each of the six Kona IEA stations. Right: Trawl catch composition, with circles scaled by catch volume. Volumes are the average of two nightly tows, with the exception of the east-central and northwest stations, where one nightly tow at each site was compromised by cookie cutter shark bites to the trawl's cod end. Black dots show locations of cetacean vocalizations. The dashed lines indicate transects.