Geology topics

Tyronne F. Donnelly

Publications and source records attributed to Tyronne F. Donnelly.

5 recordsLinked to original sources

USGS2022

Abundance and distribution of eelgrass (Zostera marina) and seaweeds at Izembek National Wildlife Refuge, Alaska, 2007–10

Eelgrass ( Zostera marina ) meadows are expansive along the lower Alaska Peninsula, supporting a rich diversity of marine life, yet little is known about their status and trends in the region. We tested techniques to inventory and monitor trends in the spatial extent and abundance of eelgrass in lagoons of the Izembek National Wildlife Refuge. We determined if Landsat imagery could be used to assess eelgrass spatial extent in shallow (less than 4 meter water depth) coastal waters of the refuge. We determined that this seagrass could be differentiated using Landsat imagery from other cover types (that is, channels and unvegetated tidal flats) with a high degree of accuracy (greater than 80 percent) in Izembek and Kinzarof Lagoons. Eelgrass meadows represented the largest cover type in Izembek (about 16,000 hectares) and Kinzarof (about 900 hectares) Lagoons, comprising between 45 and 50 percent of the spatial extent of these lagoons, respectively. When compared to estimates of spatial extent of eelgrass from previous studies, our results suggest little change in the spatial extent of eelgrass in Izembek Lagoon during the 28-year period 1978 through 2006. Preliminary mapping of eelgrass in other embayments indicated that this seagrass was also expansive in Big Lagoon (about 900 hectares; or 34 percent of the lagoon area) and Hook Bay (about 900 hectares; or 36 percent of the bay area) but not in Cold Bay (about 100 hectares; less than 5 percent of the bay area). We conducted an embayment-wide point sampling technique to assess aboveground biomass and distribution of eelgrass and seaweeds and presence of six macro-invertebrates during a 4-year period (2007–10). We determined that, when present, mean aboveground biomass of eelgrass was greater in Kinzarof Lagoon (182.5 plus or minus 12.1 grams dry weight per square meter) than in Izembek Lagoon (152.1 plus or minus 7.1 grams dry weight per square meter) in 2008–10, possibly reflecting the warmer sea temperatures and higher salinities found on the Gulf of Alaska side of the Alaska Peninsula. Seaweeds were more abundant in Kinzarof Lagoon than in Izembek Lagoon, surpassing aboveground biomass of eelgrass in both lagoons in 2008. Gastropods (4 percent of all points) and Caprella shrimp (25 percent) were the most common of the six macro-invertebrates surveyed in Izembek Lagoon, and Telmessus crab was the most common macro-invertebrate in Kinzarof Lagoon.

Alaska↗

USGS2022

Distribution of eelgrass (Zostera marina) in coastal waters adjacent to Togiak National Wildlife Refuge, Alaska

Declines in the distribution and abundance of seagrasses worldwide have prompted a need for baseline distribution maps of eelgrass ( Zostera marina ) in Alaska. We used high-resolution digital-color aerial photography and multi-spectral satellite imagery to map the distribution and spatial extent of eelgrass at 21 sites in coastal waters adjacent to Togiak National Wildlife Refuge (TNWR) in northwestern Bristol Bay and southern Kuskokwim Bay. The total spatial extent of eelgrass meadows was estimated to be 6,489 hectare (ha) almost equally divided between Bristol Bay (3,001 ha) and Kuskokwim Bay (3,488 ha). The four largest eelgrass beds occurred in Chagvan Bay (1,933 ha), the north side of Hagemeister Island (1,168 ha), Goodnews Bay (874 ha), and Nanvak Bay (599 ha). This report provides key baseline data useful for establishing a monitoring plan to assess trends in eelgrass along the coast of TNWR.

Alaska↗

USGS2022

Eelgrass (Zostera marina) and Seaweed Abundance along the Coast of Togiak National Wildlife Refuge, Alaska, 2008–10

We conducted a point-sampling survey to determine eelgrass ( Zostera marina ) and seaweed abundance in coastal waters adjacent to Togiak National Wildlife Refuge, Alaska, in July 2008–10. Eelgrass was known to be abundant in protected embayments of the southeastern Bering Sea and near the Togiak National Wildlife Refuge, but prior to this study, no systematic ground surveys had been conducted in these areas. We determined mean aboveground biomass of eelgrass to be highly variable among years observed, ranging from 32–72 grams dry weight per square meter (g/m 2 ) during successive years in Nanvak Bay and among the studied embayments in 2010: 47±4 g/m 2 in Nanvak Bay, 69±7 g/m 2 in Chagvan Bay, and 74±15 g/m 2 in Goodnews Bay. Seaweed density, abundance, and frequency scores were also highly variable among years and among embayments and were lower for seaweeds than for eelgrass in Nanvak and Chagvan bays, but not in Goodnews Bay. For all bays, mussels ( Mytilus spp.) and gastropods were the most common macro-invertebrates detected during surveys, whereas sea stars, crabs, and sponges were not observed in the embayments.

Alaska↗

USGS2022

Eelgrass (Zostera marina) and seaweed assessment Alaska Peninsula-Becharof National Wildlife Refuges, 2010

We conducted the first assessment of eelgrass and seaweed distribution and abundance along the coast of the Alaska Peninsula-Becharof National Wildlife Refuges in Chignik Lagoon and Mud Bay. Areal extent of eelgrass, as determined from remote-sensing techniques, was estimated to be 2,414 hectares in Chignik Lagoon and 188 hectares in Mud Bay, and eelgrass was the dominant marine macrophyte in each of the embayments. During an embayment-wide point survey of Chignik Lagoon, eelgrass and seaweeds were observed on 76 and 62 percent of survey points, respectively. Average percent cover was greater for eelgrass (82 percent) than for seaweeds (37 percent) when each was present at a survey point. In contrast, eelgrass and seaweeds were distributed nearly equally in Mud Bay, occurring on 64 and 70 percent of the points, respectively, and when present, cover of eelgrass and seaweeds were 70 and 60 percent, respectively. Brown and red seaweeds, such as Polysiphonia pacifica, Saccharina latissima, Neorhodomela oregona, and Eudesme borealis, were the most common seaweeds in Chignik Lagoon, while green seaweeds, particularly Kornmannia leptoderma and Cladophora sericea, were dominant in Mud Bay. Standing crop of eelgrass was 44 percent greater in Chignik Lagoon (98.0±6.4 grams dry weight per square meter) than in Mud Bay (68.3±6.7 grams dry weight per square meter) in 2010. Five types of macro-invertebrates were assessed during the point survey. At least one of these macro-invertebrates was observed on 45 percent of points in Chignik Lagoon and 64 percent of points in Mud Bay. Gastropods were the most common of the macro-invertebrates, occurring on 40–57 percent of points in each of the embayments. This assessment of eelgrass and seaweeds can serve as a baseline for determining future changes in the distribution and abundance of these marine macrophytes in Chignik Lagoon and Mud Bay.

Alaska↗

USGS2022

Inventory of eelgrass (Zostera marina) and seaweeds at the end of the Alaska Peninsula, August–September 2012:

Coastal communities in Alaska are undergoing rapid environmental change from increasing temperatures and baseline data are needed to monitor potential impacts. We conducted the first surveys of the abundance and distribution of eelgrass ( Zostera marina ) and seaweeds in the western part of Izembek National Wildlife Refuge at the end of the Alaska Peninsula. Six embayments and two offshore islands were surveyed in August–September of 2012. Biotic (percent cover of eelgrass/seaweeds, presence/absences of five sessile invertebrates), and abiotic (water temperature, salinity, and depth) data were recorded at 257 survey points (range =9–74 points per site) across all sites. Twenty-two genera/species of seaweeds were identified at the six embayments. New seaweed species for the offshore islands of Sanak and Caton were added to an existing seaweed collection accessioned at the University of British Columbia Herbarium. We also collected samples of eelgrass to be accessioned at U.S. Geological Survey, Alaska Science Center-Molecular Ecology Laboratory, for future genetic analyses. Fifty-three species of birds and 13 species of mammals were observed and recorded during the survey period.

Alaska↗