Kachemak Bay

Ecology & Conservation

OVERVIEW OF THE BAY
There are literally two sides to the Kachemak Bay story. The following is excerpted from the KBRR management plan: 

The northern and southern sides of the watershed have dramatically different geomorphology, geology, climate, vegetation, soil, and hydrology characteristics. Hydrology also differs between the two sides. The north side of the watershed, which has gentle topography, and the head of the Bay both have much more extensive river systems than the south side of the Bay, where steep topography and glaciation limit the length of the rivers. Melting snow and rain drive the hydrologic system of the northern watershed, including the Anchor River, and determines the timing of peak flows. On the southern side, snow melt in the early summer, and glacial melt in the late summer, are the predominant influences. The rolling hills and gentle slopes of the northern side of the watershed are underlain by sedimentary rock, while the jagged glaciated peaks of the southern side are underlain by ancient bedrock.

The climates of the northern and southern sides are also rather different. The southern side is wetter, and much more snow and precipitation falls annually in Seldovia than in Homer. As a result, the wetter, steeper southern side supports the most northern reach of the temperate rain forest. In comparison, the drier, flatter northern side supports a mixed deciduous and conifer community that transitions to tundra that comprises much of the Peninsula's eastern side.

The head of Kachemak Bay is characterized by extensive tidal flats, braided drainages, and marshlands. The northern shore consists of cliffs composed mostly of sand and clay leading down to shallow mud flats. The southern shoreline consists of hard rock cliffs and deep embayments. Many islands are also found along the southern shore.

Several major glacial streams discharge into inner Kachemak Bay: Fox, Martin, Wosnesenski, and Bradley Rivers; and Sheep, Battle, Halibut, Portlock, and Grewingk Creeks. In addition, several minor nonglacial streams discharge into Kachemak Bay along the southern shore. The northern coast is drier, and only eight small nonglacial streams of limited drainage enter the inner Bay from that side. The rolling terrain behind the northwest shore suggests that river flow is controlled by precipitation. About 90% of the area immediately north of the Bay is drained by the Anchor River, discharging directly into Lower Cook Inlet.

The Homer Spit is a striking geologic feature of Kachemak Bay, and it also has a dramatic impact on the Bay's circulation. The Spit bisects the Bay into inner and outer zones. These zones differ in freshwater influence and in wave action. The outer saline Bay is a mixing basin for the cold, saline, nutrient-rich Alaskan coastal current. The Alaskan coastal current comes from the southeast via the Cook Inlet and from the glacial fresh water that drains from the Bay's tributaries. It is a high-wave-energy environment that receives the full force of swells from across the Inlet. The inner Bay has a lower salinity because the influence of freshwater tributaries is stronger in the semi-contained water found behind the Homer Spit. The inner Bay also remains calmer because the Homer Spit blocks the swells from the Inlet. Water masses from the inner and outer zones of the Bay meet during the daily tidal cycle.

SHOREBIRDS
Some 244 species of birds have been identified on and around Kachemak Bay. Kachemak Bay is the most important marine bird habitat in Lower Cook Inlet, with no comparable areas in Upper Cook Inlet. During winter months over 90% of the marine birds in Lower Cook Inlet are found in Kachemak Bay. Kachemak Bay is also important for avian feeding, nesting, rearing, and migratory staging throughout the year. The inner Bay coastline has an estimated total year-round density of 1,758 birds/km² (679 birds/mile²⁾ .

During spring migration, large flocks of sandpipers and Dunlin as well as plovers, dowitchers, godwits, yellowlegs, and Whimbrel prefer the inner Bay where there is a greater abundance of Macoma. The rocky islands in the Bay, as well as the rocks protecting the harbor tend to attract turnstones, Surfbirds, Black Oystercatchers, and Wandering Tattlers. Large numbers of Red-necked Phalarope will be on the water.
 

CLAMS
Kachemak Bay has substantial populations of clams, including Pacific littlenecks, butter clams, surf clams, various cockles, razor clams, and several Macoma (baltic, stained, chalky, oblique, and bent-nosed.) Hard-shelled clams can be found in the lower intertidal region on protected gravel-sand-mud beaches. Soft-shelled clams are usually found in areas of mixed sand and mud, or mud and gravel.

THREATS
With the exception of about half of the Homer Spit, much of the shorebird habitat in Kachemak Bay has little disturbance from human activity. However, the Cook Inlet region receives a lot of geologic activity. Glaciers, volcanoes, earthquakes, and storms have all left their mark. The most significant recent event was the 1964 earthquake which lowered Kachemak Bay by a few feet. However, because of isostatic (glacial) rebound, the area is slowly rising, which will alter intertidal areas.

The quality of the Kachemak Bay habitat was threatened by oil leases in the 1970s. However, then-Governor Hammond cancelled the leases. Although the Exxon Valdez oil spill occurred hundreds of miles from here, some oil did stain Kachemak Bay waters. Shipping poses possible threats to Kachemak Bay, which is considered a port of refuge because disabled and leaking ships may try to seek refuge in the protected waters of the inner bay. Also, foreign ships frequently anchor in the Bay and could introduce invasive species.

RESEARCH
The Kachemak Bay area has significant scientific facilities to study and monitor the ecological condition of the Bay. KBRR and the Alaska Maritime National Wildlife Refuge share a large facility and visitor’s center in Homer. State resource management agencies also have a presence in Homer. The University of Alaska Anchorage - Kenai Peninsula College has a campus in Homer. NOAA and the University of Alaska Fairbanks operate the Kisitsna Bay Lab on the south side of the Bay.