Outer Coast Research Articles

Resource partitioning and competition for shells between intertidal hermit crabs on the outer coast of Washington.

Resource partitioning was quantified for 6 species of intertidal hermit crabs in the genus Pagurus, that occur on the outer coast of Washington. This, together with field evidence of shell shortage and with laboratory experiments to quantify the mechanism of interactions for shells, allowed estimation of the relative intensities of inter-and intraspecific competition between these species. The findings were that: (1) the magnitude of intraspecific competition was greater than any single interspecific competitive effect for all of the species; and (2) the relative proportion of intraspecific competition was greater for the middle and upper intertidal species than for the lower intertidal species. Studies at several outer coast sites supported these generalizations. Both of these findings are consistent with the hypothesis that competitive divergence has occurred in the past. The structure of the outer coast hermit crab assemblage is compared with that of the San Juan Archipelago hermit crab assemblage. Differences between the two do not seem to be the result of adaptive responses to the presence of more competing species in the former group.

The fall (and rise) of central Vancouver Island: 1930–1985

Levelled height differences obtained from first-order vertical control surveys between 1930 and 1984 indicate large apparent elevation changes along the east coast of central Vancouver Island, British Columbia. The levelling survey following the 1946 earthquake (M = 7.3) indicated relative subsidence, likely coseismic, of up to 80 mm for the northern third of the 130 km traverse between Comox and Campbell River. Subsequent surveys indicated relative uplifts within this region at rates averaging 1 mm/year (1946–1977) and 5 mm/year (1977–1984). Tilting along a 90 km traverse across central Vancouver Island between Gold River and Campbell River is not well defined because of uncalibrated magnetic errors present in the 1976–1978 baseline data. Minimal estimates indicate a possible average uplift rate of 1–2 mm/year for the east coast region with respect to the outer coast between 1976 and 1985.Taken at face value, these data are consistent with the crustal deformation sequence expected for an earthquake cycle. The coseismic subsidence has been followed by gradual postseismic recovery totalling 30 mm over 30 years. The apparent recent acceleration of this uplift rate to 5 mm/year could mark a stage of more rapid strain accumulation prior to a seismic event. The sense of tilting, principally upwards to the northwest, is difficult to reconcile with two-dimensional, northeast subduction. If this tilting is being generated at depths directly by the subduction process, it implies that the northern part of the survey area overlies a locked or currently more resistive subduction zone. Alternatively, elastic strain accumulation within the crust across the Beaufort Range (or a subparallel) fault preceding right-lateral strike-slip rupture could also lead to the observed tilt pattern.

Rainfall and the interaction of microclimate with larval resources in the population dynamics of checkerspot butterflies (Euphydryas editha) inhabiting serpentine grassland.

The interaction of host plant phenology and microclimatic heterogeneity was examined to determine its role in the population dynamics of checkerspot butterflies, Euphydryas editha, inhabiting serpentine grassland in California's outer Coast Range.Within the 2-3 hectares inhabited by a population of E. editha (Jasper Ridge Area H), microclimatic differences resulting from topographic heterogeneity largely determine the temporal and spatial pattern of senescence of the larval host plants, Plantago erecta and Orthocarpus densiflorus. Survival of larvae from hatching to diapause is extremely low as a result of unpredictable variation in the timing of larval development relative to the timing of host plant senescence, both of which are mediated by microclimatic patterns. During this study, population H declined to near extinction as a result of two consecutive years of record rainfall that apparently disrupted the tenuous temporal relationship between larval development and plant senescence. Retarded development of post-diapause larvae led to a late and extended flight season and delayed egg production; this in turn resulted in massive mortality of pre-diapause larvae due to starvation because host plant senescence occurred before larvae became large enough to enter diapause. Adult population size the following spring was the smallest in 25 years of study. This work emphasizes the importance of microclimatic heterogeneity for understanding population-level processes in small ectothermic animals and underlines the potential importance of such heterogeneity in the establishment of reserves designed to protect such animals.

Evidence for Great Holocene Earthquakes Along the Outer Coast of Washington State

Intertidal mud has buried extensive, well-vegetated lowlands in westernmost Washington at least six times in the past 7000 years. Each burial was probably occasioned by rapid tectonic subsidence in the range of 0.5 to 2.0 meters. Anomalous sheets of sand atop at least three of the buried lowlands suggest that tsunamis resulted from the same events that caused the subsidence. These events may have been great earthquakes from the subduction zone between the Juan de Fuca and North America plates.

87:6298 Evidence for great Holocene earthquakes along the outer coast of Washington State: Atwater, B.F., 1987. Science, 236(4804):942–944

87:6298 Evidence for great Holocene earthquakes along the outer coast of Washington State: Atwater, B.F., 1987. Science, 236(4804):942–944

Tsunami warning system for the pacific coast of Canada

Abstract The Tsunami Warning System for the Pacific Coast of Canada, which is part of the International Tsunami Warning System for the Pacific Ocean, is reviewed and major problems are identified. The efficiency of the present warning system is examined in view of the prediction by the international seismological community that major earthquakes are likely to occur in various seismic gaps around the Pacific rim in the near future. Whereas the present system is more or less adequate for the outer coast, at present there is no warning system for tsunamis generated locally in the Straits of Juan de Fuca and Georgia, or in Puget Sounds.

The effect of temperature on development and reproduction in Chorda filum and C. tomentosa (Phaeophyta, Laminariales) from Nova Scotia

The occurrence of sporophytes of Chorda tomentosa and C. filum in the southern Gulf of St. Lawrence was correlated with the field temperature regime. Temperature tolerances of gametophytes and young sporophytes of both species were tested in culture, using isolates from both the gulf and the outer Atlantic coast of Nova Scotia. Chorda tomentosa sporophytes appeared in late winter when the water surface was frozen, were fertile from April to June, and died when water temperature approached 20 °C. In culture, sporophytes tolerated −1 to 15 but became moribund at 20 °C. Gametophytes in constant temperature reproduced readily at 5 °C, occasionally at 0 and 10 °C, but not at higher temperatures; they survived to 24 °C. After 6 months in dim light at 10 °C some gametophytes also released gametes at 15 °C. Sporophytes of C. filum appeared in the field in spring after the water temperature had risen above 1 °C and persisted through the warm months. New sporophytes appeared in the autumn after the water temperature dropped below 15 °C but did not survive the winter. In culture, sporophytes died at −1 and 28 °C and survived between 0 and 24 °C. Gametophytes reproduced readily from 5 to 12, rarely at 0 and 15 °C, and not at higher temperatures. Gametophytes of both species survived 5 months in 0 ± 2 °C, [Formula: see text].

Late Quaternary glacial and sea-level events, Clements Markham Inlet, northern Ellesmere Island, Arctic Canada

Clements Markham Inlet cuts into the Grant Land Mountains of the northernmost coast of Ellesmere Island. The head of the inlet is bounded on three sides by mountain ice caps that surround lowlands mantled by extensive raised marine deposits. Fieldwork and mapping of late Quaternary sediments were used to determine the limits of past glaciations and the nature of ice retreat from the inlet head. Forty-five radiocarbon dates on driftwood and marine shells provide a deglacial chronology and document related sea-level adjustments.High-level ice-marginal meltwater channels and mountain summit erratics indicate that ice once inundated all of Clements Markham Inlet. During at least one of these undated glaciations, ice flowed unconstrained by the local topography. In contrast, the most recent glaciation involved confluent trunk glaciers, which terminated near the head of the inlet. Beyond this terminus, smaller glaciers entering the sides of the inlet debouched into a glacioisostatically depressed sea (full glacial sea). Retreat from the last glaciation is documented by moraines, kame terraces, and ice-contact deltas.Inside the ice limit at the head of the inlet, sections commonly show that a marine transgression occurred immediately after the retreat of the ice. Conversely, sections outside the last ice limit, along the sides of the inlet, show complex intercalations of marine and glacigenic sediments. These indicate proximal ice-front conditions where small valley glaciers locally contacted the sea.The oldest date on the last ice limit is 9845 BP. After this, slow retreat was in progress, and some glaciers were within 6 km of their current positions by ca. 9700 BP. At the head of the inlet, the mouths of the confluent valleys became ice free by 8000 BP. After 8000 BP, glacial retreat accelerated greatly, so that the entire lowland became ice free within 400 years.Relative sea-level curves from the inlet indicate ice-load changes that confirm this pattern of ice retreat. Outside the last ice limit, the full glacial sea reached 124 m asl by at least 10 000 BP. Emergence from this sea occurred slowly between at least 10 000 and 8000 BP (0.72 m 100 year−1). This period was followed by "normal" rapid postglacial emergence, which decelerated to the present.The marine limit of the full glacial sea rises from 92 m asl, at the outer coast, to 124 m asl near the last ice limit at the head of the inlet. Initial emergence from the full glacial sea occurred simultaneously throughout the inlet. On the proximal side of the last ice limit, the marine limit descends in the up-ice direction and becomes progressively younger. Individual strandlines tilt up in a southwesterly direction towards the central Grant Land Mountains, suggesting a former centre of glacio-isostatic loading in that area.

Carbon and oxygen stable isotope values in shells of Mytilus edulis and Modiolus modiolus from holocene raised beaches at the outer coast of the varanger Peninsula, North Norway

The amplitudes of isotopic temperatures based on the stable isotope values of the calcite in profiles from shells of Mytilus and Modiolus from Holocene raised beaches, earlier dated, and in recent Modiolus shells were shown to correspond to the observed annual amplitude of the surface water in the area. The relation between δ 13C and δ 18O values shows that the ocean water has been mixed with fresh water from the rivers at the coast where the molluscs lived. The isotopic temperatures were therefore based on this ratio. No clear differences in annual temperatures could be demonstrated within the period studied of about 4500 years.

Benthic community—water column coupling during the 1982‐1983 El Niño. Are community changes at high latitudes attributable to cause or coincidence?1

The 1982–1983 El Niño generated a strong signal which diminished poleward. Although water mass properties were clearly influenced at 48°N, no effects were identified on a rocky intertidal community which could unambiguously be attributed to El Niño. The analyses included long term studies of the upper limits to the distribution of a red alga (7 years) and two species of mussels (14 years). No effect was identified on the recruitment, mortality, or growth of a brown alga, Postelsia. Major sea urchin recruitments have occurred on the Washington outer coast four times in the last 22 years, only two of which have been El Niño events, although all were in years of warmer than average water. Major (extreme) episodes of mussel bed disruption occurred immediately after the latest El Niño, but also during a cold water winter (1975–1976). The data suggest that it is difficult to distinguish the influence of even a potentially strong perturbation against a biologically variable background when a long term data base exists.

Delaciation of the Prince Rupert – Kitimat area, British Columbia

Late Wisconsinan sediments in the Prince Rupert – Kitimat area of west-central British Columbia were deposited in an isostatically depressed marine environment affected by grounded tidewater glaciers. The most common sediments are (1) massive, bedded, and laminated muds, and (2) stratified sand and gravel. The former are accumulations of clay- and silt-size detritus transported in suspension from the mouths of meltwater streams and possibly in turbidity flows generated by submarine slope failures. The muds locally contain scattered ice-rafted stones, fossil marine molluscs, and foraminifera. The main sand and gravel deposits are elevated deltas, including both small incised fan-shaped forms at the margins of the main valleys and enormous ice-contact delta–sandur complexes on the floor of Kitsumkalum–Kitimat trough, the largest valley in the study area.Delaciation occurred by downwasting and complex frontal retreat between about 13 000 and 10 000 BP. The open outer coast became ice free first, in response to wholesale destabilization of the western periphery of the Cordilleran ice sheet by eustatically rising seas. Glaciers retreated rapidly by calving and soon were confined to fjords and mountain valleys; thereafter, they receded more slowly. The distribution of glaciomarine mud and raised deltaic deposits in Kitsumkalum–Kitimat trough indicates that retreat there was nonuniform, with intervals of catastrophic retreat separated by periods during which glacier snouts were relatively stable.Delaciation was accompanied and followed by rapid isostatic uplift. In Kitsumkalum–Kitimat trough, shorelines fell from about 200 m elevation at 10 500 BP to present sea level at about 8000 BP; about half of this fall occurred in perhaps as little as 500 years.

Quaternary Glaciomarine Sedimentation Interpreted from Seismic Surveys of Fiords on Baffin Island, N.W.T.

Seismic reflection surveys using a compressed air source in nine fiords on Baffin Island provide information on the amounts of sediment deposited and the relation of sedimentation to events during late Quaternary glaciation. Five sedimentary facies can be recognised in the seismic records: (A) a basal facies of ice contact glacial sediment including moraines and deformed, stratified, glaciomarine sediment, (B) a lower glaciomarine facies of well-stratified sediment deposited in an ice-proximal environment, (C) a facies of acoustically transparent sediment deposited in a lower energy environment farther from sources of glacial sediment, (D) an upper, well-stratified facies similar to facies B and also interpreted as ice-proximal, and (E) a thin facies of modern sediment on top of the other materials. These facies are tentatively correlated with glacial events on eastern Baffin Island. Facies A and B are associated with the retreat of glaciers from the outer coast and continental shelf of Baffin Island during the early Foxe Period (>50,000 BP). Facies D is associated with the readvance of glaciers to form the moraines of the Baffinland drift during the Cockburn Substage of the Early Holocene. The intervening Facies C is associated with lower energy conditions and less sediment input in a long period between these events, and Facies E with the present environment in the fiords.Key words: Baffin Island, fiords, sedimentology, continuous seismic profiling, Quaternary glaciation

Herbivory and the Seasonal Abundance of Algae on a High Intertidal Rocky Shore

This paper examines the contribution of herbivory to seasonal variations in algal coverage at the uppermost intertidal levels of a rocky shore on the outer coast of Oregon, USA. In this habitat, simple, fast—growing algae are abundant during wetter, less sun—exposed, and cooler weather of the winter months, but disappear in the drier, sunnier, and warmer conditions of the summer. Acmaeid limpets, the predominant herbivores in the habitat, are present throughout the year. Previous studies of the high intertidal zone have suggested that physical stresses alone prevent the survival of algae through the summer months, and that grazing affects algal abundance when physical conditions are more benign. To test these hypotheses, cageless methods were used to exclude the limpets from plots on the uppermost intertidal rocks. The experiments were repeated at 3—4 mo intervals over a period of several years. This partial reduction in herbivory resulted in the development and persistence of dense covers of algae through the summer months, as well as increasing algal abundance during the other times of year. Apparently the primary cause of the seasonal fluctuations in algal abundance is variation in rates of algal production rather than change in absolute rates of algal loss to herbivory or physical stresses. Evidence from this study and the literature indicates that the limpets in this habitat are probably consuming more, not less, algae in the winter months. However, higher rates of algal production in winter more than compensate for the increased herbivory, and the algae become more abundant. During the summer, drier conditions cause rates of production by the algae to fall below rates of consumption by limpets, and the limpets remove most of the standing crop of algae. Thus, increased grazing pressure coincides with increased physical stress. To be a perennial or summer annual in this habitat, an alga not only must be resistant to desiccation, insolation, and high temperatures, but also must be inaccessible to herbivores or be resistant to herbivory. In the uppermost intertidal zone, the abundance of algae in winter evidently depends on the pattern of changes in primary production over the entire year. Scarcity of forage in the summer months reduces populations of the resident limpets, and the favorable conditions for primary production in winter months allow the transient species of algae to establish rapidly, grow, and reproduce before the populations of limpets recover. If even the most favorable physical conditions for algal growth remained constant through the year, the transient algae would probably disappear. It is speculated that under present conditions the establishment of perennial algae in this habitat is limited by the intensity of herbivory in the summer and by competition with transient algae in the winter. If this is correct, less fluctuating physical conditions, even if severe, would change the species composition of this high intertidal community by favoring the establishment of perennial algae.

The Alpine Fault, New Zealand, near Milford Sound and to the southwest

AbstractFrom 70 km northeast of Milford Sound (44.14° S, 168.55° E) to the coast at Milford Sound (44.53° S, 167.83° E) the trace of the Alpine Fault is nowhere more than 1.2 km from the arc with a centre at 48.81° S, 173.20° E and a radius of 628 km (5.65° latitude). Earthquake epicentres indicate that the arc defines the position of the fault just off Fiordland's outer coast and then to near the north end of Puysegur Trench at 46.9° S, 165.25° E. Along the fault vertically to a depth of 10 km the Fiordland rocks are 0.6 Mg/m3 denser than those to the northwest. Displaced post-glacial topography at and near Milford Sound shows that the dip of the fault is southeast at 75 ± 5° and that the faulting is pure dextral at a rate of at least 46 ± 5 mm/yr.

Heterodermia sitchensis, a New Lichen from the Pacific Northwest of North America

The new species Heterodermia sitchensis is describedfrom British Columbia, Canada, where it is apparently a rare epiphyte restricted to sheltered localities at low elevations along the highly oceanic outer coast. Zeorin and atranorin are its primary phenolic constituents. Particularly interesting are the sterile, but sorediate, apothecial structures of this species. Heterodermia sitch- ensis is possibly a vicariad of the fertile H. podocarpa (BIl.) Awas. One of the lichenologically most interesting, and yet least explored, parts of North America is the coastal margin of the Pacific Northwest. Here an annual precipitation often exceeding 3000 mm combines, even at boreal latitudes, with a high de- gree of thermal oceanity to support many endemic lichen species (Ahti 1977). Recent intensive studies on the west coast of Vancouver Island, Canada, have turned up the present new species, Hetero- dermia sitchensis.

Hemioniscus balani Buchholz in northern Norway (Isopoda, Cryptoniscina)

The parasitic isopod Hemioniscus balani Buchholz is widespread and common on the outer coasts of northern Norway. Infection percentages show a clear vertical gradient, from 0 % in the high intertidal Balanus balanoides belt to a maximum (up to 70-80%) near MLW. Multiple infections are not uncommon: up to four Hemioniscus females have been found in a single host.

Drift Tube Studies of Bay-Ocean Water Exchange and Implications for Larval Dispersal

Surface water transport and larval dispersal potential within Mission Bay, San Diego, California and along the southern California coast were studied with drift test tubes. Drift tubes, released once during each season at six sites inside Mission Bay, traveled up to 173 km north and 205 km south of Mission Bay at maximum rates of 36 cm per s (north) and 50 cm per s (south). These findings were used to estimate probability of larval transport out of Mission Bay for the intertidal spionid polychaete Pseudopolydora paucibranchiata (Okuda) which occurred in the back of the bay. Outer coast drift tube returns were used to determine potential for gene flow, via larval exchange, between populations in isolated bays along the California coast. Drift tube recoveries and larval abundances in the plankton indicate that few Pseudopolydora larvae leave Mission Bay, but that longshore currents can carry those which do to other suitable bay habitats.

The Holocene vegetational development of the Godthåbsfjord area, West Greenland

Holocene pollen and macrofossil diagrams from four low arctic lakes at Godthåbsfjord are presented. Each core has been divided into radiocarbon-dated palaeovegetation zones, based on the remnants of terrestric plants. The PY zones are physiognomically similar, but differences as to the composition and frequency of species can be seen between the two lakes in the interior and the two lakes from the outer coast area. The vegetation which invaded the deglaciated soil was open but rich in species, and 64 species or genera have been determined from the pioneer stage (c. 9400 - 8000 B.P.). Open soil plants were dominating, but dwarf-shrubs entered the vegetation, with species from snow-patches and snow-covered heaths dominating in the beginning. By 8000 B.P. Salix glauca and S. herbacea immigrated, and gradually the pioneer plants and chionophilous dwarf-shrubs were decimated. This Salix-Cyperaceae stage lasted until c. 6300 B.P., when Betula nana spread all over the area within a few centuries. A Betula nana-Juniperus stage lasted until c. 3500 B.P. In the subcontinental interior this was followed by an Alnus crispa-Berula nana stage, which in turn was replaced by a Beutla nana-Ericales stage around 1800 B.P. Alnus has never been able to grow at the maritime outer coast, where Betula, Cyperaceae, Empetrum and other Ericales dominated after c. 3500 B.P. Later on, Empetrum, Cypcraceae and snowbed plants gradually spread at the expence of Betula nana. After the deglaciation the temperature increased, reaching today's values between 8000 and 7500 B.P. At which time during the coming millennia the temperature curve peaked is not known, but it may have been fairly late, presumably during the Benita nana-Juniperus stage. Major climatic changes are registered in the interior at 3900-3600 and 1800 B.P., and at the outer coast at c. 3600 and 2500-2000 B.P. From around 8000 B.P. the development of the lakes is fairly independent of the physical conditions of the surroundings, being dependent mainly on the trophic stages of the lakes. These pass through a succession: highly productive, eutrophic – less productive, mesotrophic - very poor, oligotrophic. As well as in the flora and fauna, these stages are reflected in the sediment, which at the beginning was a clay gyttja followed by a jelly-like gyttja and, finally, by a loose, watery gyttja consisting mainly of precipitated humus. Chemical analyses of one of the cores confirm the oligotrophication. The pollen influx in the pioneer stage is less than 100 grains per cm2 per year, increasing during the Hypsithermal to c. 300 in three of the lakes and c. 1000 in the richest one, but since then the influx decreases somewhat upwards. A survey of the immigration or first appearance of some species palynologically important to South and West Greenland shows big time lags in the spreading of some species, e.g. Thalictrum and Angelica, whereas others, like Empetrum and Juniperus, have a more effective dispersal capacity.

Stratigraphy, amino acid geochronology, and correlation of Quaternary sea-level and glacial events, Broughton Island, arctic Canada

Raised marine and glaciomarine terraces on Broughton Island record regional isostatic adjustments and eustatic sea-level changes. Previous workers proposed three alternative glacial and sea-level chronologies of the region. These conflicts are resolved by the stratigraphic control provided by amino acid ratios (D-allo-isoleucine/L-isoleucine) in marine molluscs collected form cliff exposures. Amino acid ratios, radiometric dates, and relative weathering measurements on geomorphological features provide a basis for regional correlations.Based upon amino acid ratios, the coastal sedimentary sequences, all part of the Broughton Island Formation, can be subdivided into six units to which informal member names have been assigned. These units delimit at least four glacial episodes during which local ice advanced around Broughton Island to the outer coast. The youngest advance is correlative with deposits that are dated > 54 000 BP, and the absolute ages of older events have been estimated from minimum uranium-series dates and amino acid data. Glacial events previously recognized as the Foxe Glaciation represent a much greater portion of the Quaternary than was previously realized.The Tuneek member, the oldest sedimentary unit on Broughton Island, consists of a bouldery, sandy clay diamicton deposited by a major pre-Foxe glacial advance(s) that occurred possibly > 500 000 years BP when ice traversed the island. Subsequent advances were deflected along the southern coast of the island through Broughton Channel. The Anigatalik member, estimated to be between 300 000 and 500 000 years old, consists of a variety of sediment types including bouldery clay diamictons and bedded, coarse sands and gravels. The Platform member represents a subsequent and extensive pre-Foxe glacial advance. It consists of a bouldery, shelly till deposited over a wave-cut platform at the north end of Broughton Island between 250 000 and 350 000 years BP. Correlative tills were deposited along the east coast by glacial ice extending around the southeast corner of the island. Relative sea level was at least 72 m asl during this time.The Cape Broughton member consists of ice-proximal sediments deposited when fiord ice was retreating from Broughton Channel approximately 150 000 – 200 000 years BP. The macrofauna and microfauna within these sediments suggest that subarctic water masses, warmer than present, were adjacent to the northeastern Baffin coast subsequent to the glacial maximum. These deposits may be correlative with a prominent moraine system on either side of Broughton Channel.The Harbour member represents the beginning of the Foxe Glaciation (as it is redefined) and delineates the last major advance of ice to the outer coast. The current best estimate for the age of these sediments is 70 000 – 130 000 years BP. At one locale, Harbour sediments overlie an organic-rich, oxidized horizon containing a pollen assemblage strongly indicative of interglacial conditions. The stratigraphy suggests that a major interglacial period preceded the Harbour advance. Organic horizons near the top of the Harbour member contain a pollen assemblage that suggests a terrestrial climate similar to that of today.The Matsaja member consists of nearshore marine sands and beach facies deposited by an early Holocene transgression to between 7 and 8 m asl that occurred approximately 8000 – 10 000 years BP. A minor transgression of 1–2 m commenced approximately 1000 years BP.

Morphological and Allozymic Variation in the Stichaeid Fish Anoplarchus Purpurescens

Morphological and allozymic variation in the stichaeid fish Anoplarchus purpurescens was compared among samples collected from open-coast localities from Alaska to California and from inner-coastal localities in Washington. We evaluated the possibility that fish from southern California (Monterey Bay southward) are genetically distinct from fish from more northern areas, which has bearing on the relevance of allozymic data from southern California fish in interpreting patterns of allozymic variation in A. purpurescens elsewhere in its geographical range. Examination of three morphological characters and 12 enzyme loci indicated the lack of genetic distinctiveness of southern California populations from more northern ones, which is consistent with the suggestion that current-mediated transport of the planktonic larvae pro- motes genetic dispersal and/or mixing among populations. The lack of genetic distinctiveness argues against the validity of a separate southern California subspecies (A. p. archolepis; Hubbs, 1927), but more importantly allows us to use the geographical pattern of muscle lactate dehy- drogenase (LDH-A) variation in California to refute the hypothesis that the A' allele is directly favored by elevated environmental temperature. Allelic frequencies in Alaska populations provide a second test of, and similarly refute, the hypothesis that elevated temperature per se selectively favors individuals with the A' allele. Although several alternative hypotheses on the evolutionary significance of LDH-A variation in A. purpurescens can be envisioned, presently a plausible one is that heterozygosity at the LDH-A locus is selectively favored by increased environmental thermal variation. This hypoth- esis is consistent not only with the geographical pattern of variation within Washington inner- coastal waters (Johnson, 1971), but also with observed changes in allelic frequencies along the outer coast both to the south (California) and to the north (Alaska). We found no significant correlation between the amount of allozymic variation (at the LDH-A and PGM loci) and morphological variation present within localities, and heterozygous fish were no more variable for meristic traits than were homozygous fish. There was no clear and consistent pattern of association between particular genotypes and morphological charac- ters. The lack of a significant relationship between enzyme and morphological traits probably is due to appreciable environmental (non-genetic) influences on the morphological characters examined, which may obscure whatever enzyme-morphological covariation exists. (Allozymes; Anoplarchus purpurescens; clines; meristic variation; natural selection; Stichaeidae.)