Effects of single and repeated experimental acid pulses on invertebrates in a high altitude Sierra Nevada stream

1. We examined responses of aquatic macroinvertebrates to pulsed acidification experiments in twelve streamside channels located in the Sierra Nevada, California. Experiment 1 consisted of a single 8 h acid addition, and Experiment 2 consisted of two 8 h acid additions administered 2 weeks apart. Replicated treatments (four reps/ treatment) consisted of a control (pH 6.5–6.7) and pH levels of 5.1–5.2 and 4.4–4.6. Invertebrate drift was monitored continuously and benthic densities were determined before and after acid addition. 2. Drift responses to pH reduction were: (i) increased drift during acidification in pH 5.2 and pH 4.6 treatment channels, often with depressed post-acidification drift in treatment channels relative to controls (exhibited by Baetis only). Depressed post-acidification drift in treatment channels appeared to be due to low benthic densities because a positive relationship between benthic and drift densities was noted for most common taxa; (ii) increased drift rates during acidification only at pH 4.6 (Epeorus, Drunella, Paraleptophlebia, Zapada, and Simulium); (iii) decreased drift at pH 5.2 and/or pH 4.6 relative to control channels (Rhyacaphila and chironomid larvae); (iv) no significant response to acidification (Ameletus, Amiocentrus, Dixa and Hydroporus). 3. A high proportion (45–100%) of acid-induced drift in Baetis, Epeorus, and chironomid larvae could be attributed to dead, drifting individuals. 4. Except for chironomids, most common invertebrates (i.e. Baetis and Paraleptophlebia) showed reduced benthic densities in treatment relative to control channels after acidification. 5. For sensitive taxa, drift was enhanced and benthic densities reduced by single (Experiment 1) and initial [Experiment 2(a)] acid pulses. Drift responses to a second acid pulse [Experiment 2(b)] were not as pronounced as those to the single or initial acid pulses [Experiments 1 and 2(a)], and the second acid pulse had no additional effect on benthic density.     

Predation and drift of lotic macroinvertebrates during colonization

Summary A field experiment was carried out to determine the effect of an invertebrate predator on the colonization and drift of benthic macroinvertebrates in experimental stream channels. Lotic invertebrates colonized four replicate channels: two controls with no predators, and two channels with low densities (2.8 m^–2) of predatory stonefly nymphs, Doroneuria baumanni (Perlidae). Immigration rates were measured at the inflow of two other channels. Drift rates of invertebrates immigrating to and emigrating from channels were measured daily, and benthic samples were collected every five days. Over a 25-day colonization period, benthic densities of Baetis nymphs and larval Chironomidae were reduced by D. baumanni. Colonization curves were fit with a power function and significantly different colonization rates were indicated for both Baetis and chironomids in predation and control channels. A predator-induced drift response was exhibited by Baetis only and this response was size-dependent. In the presence of D. baumanni, large Baetis drifted more frequently than small nymphs and, correspondingly, small nymphs were more frequent in the benthos. Net predator impacts on invertebrate densities in channel substrates were partitioned into predator-induced drift and prey consumption. These estimates suggest that predator avoidance by Baetis is a prominent mechanism causing density reductions in the presence of predators. Reductions in the density of Chironomidae, however, were attributed to prey consumption only. A rainstorm during the experiment demonstrated that stream flow disruptions can override the influence of predators on benthic invertebrates, at least temporarily, and re-set benthic densities.     

Ontogenetic changes in the drifting of four species of elmid beetles elucidate the complexity of drift-benthos relationships in a small stream in Northwest England

1. This study aimed to quantify ontogenetic changes in the drifting of Elmis aenea, Oulimnius tuberculatus, Esolus parallelepipedus and Limnius volkmari (Coleoptera: Elmidae), and to relate their drift to benthic density. Monthly samples were taken over 39 months, using three surface nets at each of two contrasting sites in a small stream: one in a deep section with abundant macrophytes, and the other in a shallow stony section. 2. Most larvae and adults were taken in the drift at night with little variation between catches in the three nets at each site. Day catches were very low, often zero. No significant relationships could be established between mean numbers in the drift catches and benthic densities. 3. When night catches were converted to drift densities (number caught per 100 m³ of water sampled), the latter were positively related to monthly losses in the benthos, but not to benthic densities. A linear regression described the relationship, and equations for the different life‐stages within each species were not significantly different from the equation for all life‐stages combined. However, drift losses were only about 0.07% of total losses in the benthos. A severe spate in October 1967 increased the number of larvae and adults in the drift, but not drift densities, except for immature adults of E. aenea, O. tuberculatus and E. parallelepipedus. 4. Key life‐stages with the highest drift density were the earliest life‐stage soon after egg hatching for E. aenea, the start of the larval overwintering period for O. tuberculatus and L. volkmari, and mature adults during the mating season for all three species. Drift density for E. parallelepipedus was too low to identify a key life‐stage. These key life‐stages corresponded with critical periods for survival in the life cycle, as identified in an earlier study in the same stream. Mortality was high during these critical periods, hence the strong relationship between drift density and benthic losses. The latter relationship was very consistent for different life‐stages within each species, and partially supported the rarely‐tested hypothesis that drift represents surplus production in the benthos.     

Macroinvertebrate drift in a Rocky Mountain stream

An extensive series of drift collections from a Rocky Mountain stream was used to investigate quantitative patterns in the taxonomic composition of drift throughout spring, summer and fall for 1975–1978. Drift was estimated by drift rate, the number of organisms drifting past a point per 24 h; and by drift density, the numbers of organisms collected per 100 m³ of water sampled.Drift densities were up to ten times greater by night than by day, and 24 h drift densities for the total fauna approached 2000 per 100 m³ in June–July, declining to <500 by autumn. Ephemeroptera, and especially Baetis, dominated the drift. Drift rates were greatest in late spring, around 10⁶ per 24 h, which are among the highest values reported for small trout streams. Drift rates declined to <10⁵ during the summer, and shifts in the taxonomic composition are described.Multiple regression analysis of the relationship between drift rate and density, and the independent variables discharge, benthic density and temperature, showed that discharge typically was a significant predictor of 24 h drift rate, usually the best single predictor. In contrast, 24 h drift density most frequently was independent of discharge, indicating that this measure tends to correct for seasonal variation in discharge, as suggested in the literature. However, this was not invariably true. Drift density significantly correlated with benthic density in five of eight taxa inspected, thus seasonal declines in the benthos probably accounted for parallel declines in drift density.     

Field experiments on the relationship between drift and henthic densities of aquatic insects in tropical streams (Ivory Coast). III Trichoptera

SUMMARY. 1. Based on in situ gutter trials we related the drift of caddis flies to their benthic densities and to various abiotic factors in streams in the Ivory Coast (West Africa). Members of the families Hydropsychidae, Philopotamidae. Hydroptilidae and Leptoceridae were considered in detail.
2. The drift of larvae peaked at night in both early and late larval instars.
3. Drift of a larval group (a certain instar, species or higher taxon) was more often related to the benthic density of other larval groups than to its own benthic density.
4. Self-regulation of an upper benthic density of a larval group by emigration through drift was not statistically evident.
5. There was no straightforward relationship between drift and abiotic factors.
6. Drift rates differed between taxa as well as between larval instars (size groups) within a taxon. Newly hatched larvae had very high drift rates, whereas the last larval instar usually had the lowest drift rate.
7. We related these results to the violently fluctuating discharge of the streams in the study area and the consequent variability of space for lotic insects.
8. Drift estimates, made at the same time as a monitoring programme on possible side-effects of insecticides (Onchocerciasis Control Programme), failed to reflect benthic densities except in the night drift of Hydropsychidae.     

The relation between invertebrate drift and two primary controls,discharge and benthic densities,in a large regulated river

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Invertebrate drift and benthic community dynamics in a lowland neotropical stream, Costa Rica

In this study we quantified invertebrate drift and related it to the structure of the benthic community, over a 6–8 month period, in a 4th-order tropical stream in Costa Rica. Relative to reports from similar-sized temperate and tropical streams, drift densities were high (2-fold greater: mean 11.2 m⁻³; range 2.5–25 m⁻³), and benthic insect densities were relatively low (>3-fold lower: mean 890 m⁻²; range 228–1504 m⁻²). Drift was dominated by larval shrimps that represented more than 70% of total drift on any given date; the remaining 30% was composed of 54 insect taxa. Among insects, Simuliidae and Chironomidae (Diptera) and Baetidae, Leptohyphes and Tricorythodes (Ephemeroptera) comprised 24% of total drift. Drift periodicity was strongly nocturnal, with peaks at 18:00 h (sunset) and 03:00 h. Our results, and those of previous experiments in the study stream, suggest that nighttime drift is driven by the presence of predatory diurnal drift-feeding fishes and nocturnal adult shrimps. There were no clear seasonal patterns over both ‘dry’ and wet seasons, suggesting that benthic communities are subject to similar stresses throughout the year, and that populations grow and reproduce continuously. This revised version was published online in July 2006 with corrections to the Cover Date.     

Swimming Behaviour of <Emphasis Type="Italic">Chironomus acerbiphilus</Emphasis> Larvae in Lake Katanuma

We conducted a seasonal survey of the swimming behaviour of Chironomus acerbiphilus larvae in volcanic Lake Katanuma from April 1998 to December 2001. Swimming C. acerbiphilus density was much higher than other chironomid species in lakes. All C. acerbiphilus larvae (1st through 4th instars) swam, but the earlier instars (especially the 1st) had the greatest densities and fluctuations. First instars were never found in the benthic population. This result indicates that the 1st-instar larvae are planktonic. Low water temperature (below about 10 °C) resulted in the seasonal disappearance of swimming chironomid larvae. Chemical factors – oxygen depletion or presence of hydrogen sulfide – also restricted the distribution of swimming and benthic larvae. Larvae were distributed only in the oxygen-rich part of the lake bottom and swam only in the oxygen-rich layer of the water column. The density of older swimming C. acerbiphilus (3rd and 4th instars) tended to increase with increasing benthic larval densities. The chemical stress of oxygen depletion or presence of hydrogen sulfide during holomixis within and after the stratification period leads to conspicuous swimming behaviour of benthic C. acerbiphilus larvae. Almost all C. acerbiphilus larvae died on this occasion.     

Using spatial, seasonal, and diel drift patterns of larval Lost River suckers Deltistes luxatus (Cypriniformes: Catostomidae) and shortnose suckers Chasmistes brevirostris (Cypriniformes: Catostomidae) to help identify a site for a water withdrawal structure on the Williamson River, Oregon

A small irrigation diversion dam near Chiloquin, Oregon, was removed and replaced with a pump station to improve fish passage for Lost River suckers (Deltistes luxatus) and shortnose suckers (Chasmistes brevirostris) entering the Sprague River on their spawning migrations. During the developmental phase of the pump station, a need was identified to better understand the larval drift characteristics of these endangered catostomids in order to reduce entrainment into the irrigation system. The spatial, seasonal, and diel distribution of drifting larvae was measured during the 2004 spawning season at two proposed sites on the Williamson River where the pump station could be located. Larval drift for both species coincided with the irrigation season making them subject to entrainment into the irrigation system. Drift occurred almost exclusively at night with larvae entering the drift at sunset and exiting the drift at sunrise. Nighttime larval densities were concentrated near the surface and at midchannel at both sites. Densities were generally greater on the side of mid-channel with greater flow. During early morning sampling we detected a general shift in larval drift from surface to subsurface drift. We also observed an increase in larval densities towards the shore opposite from the proposed pump station at the upper site whereas larval densities remained high at midchannel at the lower site. During daytime sampling, the few larvae that were collected were distributed throughout the water column at both pump sites. This study found that larvae drifting during all time periods were generally distributed further across the cross section, deeper in the water column, and closer to where the proposed water withdrawal structure would be built at the downstream site when compared to the upstream site. Recommendations were provided to locate the withdrawal facility at the upstream site and operate it in a manner such that larval entrainment would likely be minimized.     

Ontogenetic shifts in drift periodicity and benthic dispersal in elmid beetles

1. There is a paucity of information on ontogenetic changes in the dispersal of benthic invertebrates, which is an important aspect of their ecology. This study quantifies ontogenetic changes in diel periodicity in drift, and in upstream–downstream dispersal on the substratum for Elmis aenea, Oulimnius tuberculatus, Esolus parallelepipedus and Limnius volkmari (Coleoptera: Elmidae). Three drift nets were emptied every 3 h over 24 h in each month (October 1965–December 1968) at two contrasting sites: one in a deep section with abundant macrophytes, the other in a shallow stony riffle. Comparisons of periodicity between life‐stages of the same species were limited to months when numbers in the drift were highest. Dispersal was evaluated in six experimental stream channels, placed above the stream, with initial numbers of each life‐stage varying from 20 to 80. 2. Drift numbers were always highest at night with few or no animals in the day samples. Ontogenetic shifts in diel periodicity were similar for all four species. Drift catches were similar throughout the night for the early and intermediate larval instars and for mature adults, but were highest in the early hours of the night with a gradual decline thereafter for later larval instars and immature adults. These patterns were unaffected by a severe spate, even though drift numbers increased considerably. 3. Dispersal was density‐independent; the number of dispersing animals was a constant proportion of the initial number for each life‐stage. The relationship between dispersal distance and the number of animals travelling that distance was well described by an inverse power function. Median and maximum distances (m day^?1) were estimated for each life‐stage. 4. Ontogenetic shifts in dispersal in the stream channels matched those shown in diel drift periodicity. For all four species, the later larval instars and immature adults showed little movement in either direction, whereas early and intermediate larval instars and mature adults dispersed predominantly upstream, adults travelling further than any other life‐stage. 5. Ontogenetic shifts in diel drift periodicity and dispersal were related to seasonal changes in drift density and critical periods in the life cycle. Such shifts have not been quantified in other stream invertebrates, but should be considered when evaluating the role of dispersal in their population dynamics and their colonization ability.     

Fish predation affects the structure of a benthic community

1. We conducted an experimental study of predation by benthivorous fish on a natural community of stream invertebrates using a reach‐scale approach. Over a 2‐year period (experimental phase), the benthic invertebrate community of a stretch containing two species of benthivorous fish was compared with a fishless stretch. Thereafter, all fish were removed and benthic community structure was analysed again to account for natural differences between the two stretches (reference phase). 2. Benthivorous fish at the moderate densities investigated did not affect total benthic biomass or density, but did alter species composition. In addition, the fish effect differed between pool and riffle habitats, with larger effects in the pools indicating a habitat‐specific predation effect. In the reference phase, when all fish were removed from the stream, the difference between the two stretches was reduced. 3. The benthivorous fish reduced the densities of four taxa (Pisidium sp., Dugesia gonocephala, Gammarus pulex, Limoniidae), representing 29% of total biomass. It is possible that density reductions of other species were masked by prey migration despite the relatively large spatial scale. Indeed, higher drift activity in the upstream fishless stretch could have increased the density of Baetis rhodani in the fish stretch, as indicated by the results of a drift model. 4. Our results provide insights into stream food web ecology because fish predation showed effects even in a natural system where habitat complexity was high, environmental factors were highly variable and many predator and prey species interacted and because benthivorous fish were the focus, whereas the majority of previous predation experiments in streams have used drift‐feeding trout.     

Drift and upstream movement in Yuccabine Creek,an Australian tropical stream

Drift and upstream movement were monitored over 14 months in a seasonal upland tropical stream in northeastern Australia. There were distinct seasonal pulses in the drift with variable peak levels in the summer wet season and low more stable levels during the dry season. Drift density ranged from 0.36 to 3.98 animals per m³ (monthly mean = 1.26). There was no correlation between drift density and either benthic density or stream discharge. In the absence of catastrophic drift, drift was dispersive, not depletive in the wet season. A total of 121 taxa were caught in the 14 drift samples. Most taxa had nocturnal maximum drift levels with a peak immediately after sunset, a pattern apparently related to level of light and not temperature. Compensation for drift by upstream-moving nymphs and larvae was least during the wet season and increased during the dry season to a peak of 27% by numbers. Mean compensation was 8.2%. It is suggested that apart from in the wet season when an animal may drift substantial distances, most riffle animals will spend their larval lives in one small stretch of stream.     

Commercial potential of seaweeds from St Lawrence Island,Alaska

This study assessed the possibility of using drift and subtidal seaweeds from St Lawrence Island, Alaska (lat. 63°N) for sale by the native population after simple processing. Over 125 km of coastline were surveyed for distribution of both drift and subtidal seaweeds. Drift seaweed wet weight densities ranged from 0.2 to over 9 kg m⁻², with an average of over 4 t km⁻¹ in the areas sampled. Attached, benthic seaweed densities ranged from 0.15 to 0.32 kg m⁻². Thirty and 35% of the biomass was composed of Agarum cribrosum and species of Laminaria, respectively, both as drift and as benthic seaweed. Data from tagged Laminaria indicated that growth rates were relatively slow for most of the year. The drift seaweed resource on the coasts south and west of the city of Gambell appeared to have good potential for a small-scale commercial harvest. (*author for correspondence)     

Drift behaviour and microhabitat selection in the preimaginal stages of Simulium chutteri (Diptera Simuliidae)

The aquatic stages of the cattle biting pest, Simulium chutteri Lewis utilize river flow in their dispersal and colonization behaviour. Peaks of drifting activity in S. chutteri larvae occurred in the early morning and late afternoon. It is deduced that female flies scatter eggs onto slow flowing waters upstream of rapids. Larvae hatch from drifting eggs and colonize substrates in slower flowing regions upstream of rapids, while later stage instars move into faster flowing regions within rapids where they complete their development. This microhabitat selection by S. chutteri leads to rapid attainment of large population sizes in suitable sections of river and reduces competition between different stage larvae. In their utilization of a variety of microhabitats the larvae of this species differ from co-existing simuliid species which restrict developmental stages to single habitats.Catastrophic drift was recorded for S. chutteri larvae and could be a mechanism to regulate population size.Drift of simuliid larvae off rapids was not related to benthic population densities in the rapids and was therefore not due to excessive production. It is concluded that larval drift off rapids is related to habitat disturbances associated with water flow fluctuations and the activity of aquatic predators and other animals.The distribution of S. chutteri in the Vaal River is restricted by oviposition requirements of the adult female. Knowledge of drift behaviour and water flow requirements of Simuliidae have been applied to manage the population size of S. chutteri in the Vaal River.     

Long-term patterns of invertebrate stream drift in an Australian temperate stream

1. Invertebrate stream drift was sampled bimonthly in the Acheron River, Victoria, Australia, over a period of 18 months. Replicated hourly samples were collected over a 25-h period on each sampling date. A total of 194 taxa were identified in the drift. However, total drift density was dominated by few taxa. 2. Some evidence was obtained for a seasonal pattern in drift: this was most pronounced in relative abundances of individual taxa and the composition of the drift, rather than in total drift densities. Most of the commonly collected taxa reflected the seasonal pattern of total drift. However, some of the common taxa did not. 3. A small number of taxa showed behavioral drift, with a nocturnal increase in drift densities. One species of ‘Baetis’ drifted in high densities over short periods of time around dusk and dawn. It did not drift in higher densities during the night than during the day. The results emphasize the need for drift studies to be more rigorously designed than is typically the case.     

Invertebrate drift in a large, braided New Zealand river

1. The spatio-temporal patterns of drifting macroinvertebrates in a large, braided New Zealand river were determined by sampling with drift nets, seasonally, for 1 year. 2. Drift densities were greatest in autumn, and at night in all seasons except winter. A greater proportion of larger animals drifted at night than during the day in all seasons. Mean annual drift densities were ninety-six animals 100m^?3 and 47 mg dry weight 100 m^?3. 3. There were relatively few taxa in the drift, and the mayfly Deleatidium spp. comprised more than 85% of the drifting aquatic invertebrates in all seasons except autumn. Chironomidae and terrestrial forms were the only other groups to occur at densities of more than one animal 100 m^?3 in all seasons. 4. Drift density was positively correlated with benthic density, which in turn was adversely affected by floods, particularly during spring and summer.     

Residence time and drift patterns of larval June sucker Chasmistes liorus in the lower Provo River as determined by otolith microstructure

Estimates of age derived from daily ring counts from otoliths and capture rates of larval June sucker Chasmistes liorus were used to determine the relationship between discharge rates of the Provo River and residence time and patterns of larval drift. During 1997, larval drift occurred over a 22 day period when discharge rates were low (mean ±s.d. 3·2 ± 0·0 m³ s^?1). In 1998, larval drift occurred in two separate events over a 40 day period. Discharge was higher during the first larval drift period (19 days; 24·8 ± 1·3 m³ s^?1) and lower during the second larval drift period (17 days; 7·0 ± 0·9 m³ s^?1). In 1997, no larval fish were collected at the lowermost transect on the Provo River (nearest Utah Lake), and few larvae >21 days of age were found. During the first drift period of 1998, larval C. liorus were collected at all transects, and mean age of larvae collected between upstream and downstream transects increased by c. 7 days. During the second drift period of 1998, only a few were collected in the lowermost transects, and age did not increase with proximity to the lake. Patterns in catch and age distribution of larval C. liorus in the lower Provo River suggest that recruitment failure occurs during the larval drift period in years with insufficient discharge to transport larvae into the lake.     

Seasonal variation in benthic invertebrate recolonization of small-scale disturbances in a subtropical Florida lake

Approximately 11.5% of the littoral zone of a hypereutrophic Florida lake is disturbed by the construction of spawning beds by the cichlid fish, Sarotherodon aurea, during a single spawning season. Simulations of these beds were created during three seasons of the year to test for variation in recolonization rates and patterns in the benthic macroinvertebrate community.The seasonal variation in densities of benthic invertebrate populations suggests a direct relationship between reproductive activity and recolonization rate. Recolonization rates of the numerically dominant species, Polypedilum halterale (Diptera: Chironomidae), were much more rapid in the spring and summer than in the winter. In contrast, Hyalella azteca and Glyptotendipes paripes attained peak population densities during the winter season when Polypedilum was present in low densities. These organisms invaded the disturbed area in unusually high abundances and later declined to background levels. The final result was a winter population with densities comparable to the control (undisturbed) area, but the species composition was different.Similarity between disturbed and control communities during the winter season only reached 67% a month after disturbance, while communities during the warmer months attained nearly 90% similarity in less than 15 days. This lack of similarity during the winter indicates that disturbance, at the appropriate time, may play a role in community organization.     

Ecology and population structure of the bayou darter, <Emphasis Type="Italic">Etheostoma rubrum</Emphasis>: disjunct riffle habitats and downstream transport of larvae

The bayou darter, Etheostoma rubrum (Percidae), is endemic to the Bayou Pierre system in Mississippi. Adult and juvenile E. rubrum occupy swift, shallow riffles or runs over coarse gravel and pebble substrata. Habitat requirements of larval and post-larval stages, and the role of downstream dispersal of larvae in colonizing riffles are poorly known. The potential for movement and the high level of habitat specificity for the discontinuous riffle habitat suggest that E. rubrum may comprise a metapopulation of linearly arranged local populations. The greatest population densities of E. rubrum occur in the upper reaches of Bayou Pierre. We hypothesized that metapopulation structure of E. rubrum may include source–sink dynamics, whereby downstream areas are a sink for larvae/early juveniles originating upstream. We tested hypotheses that a transport mechanism, larval drift, occurred in E. rubrum, and that downstream riffles showed characteristics of population sinks. We captured larval stages of E. rubrum in cross-sectional and longitudinal drift nets, and rates of drift tended to increase during the day. Larval E. rubrum (n=19) occurred in samples above and below riffle areas, with no differences among longitudinal drift nets placed above and below riffles. Thus, larval drift is a viable transport mechanism. Relative abundance of adults and juveniles declined from upstream to downstream, and inter-riffle distances increased with cumulative downstream distance. However, both predictions of the source–sink hypothesis were not supported. The distribution of size classes did not change between upstream and downstream riffles nor did the mean size-adjusted body mass.     

Spatial and short-term variability of larval,post-larval and macrobenthic assemblages associated with subtidal kelp forest ecosystems in Central Chile

Identifying patterns of spatial and temporal variability in the composition of communities associated with kelp forests is critical to understand the functioning of this productive, yet vulnerable ecosystem. We used a suite of sampling methods (light attraction and airlift devices) to evaluate the variability of larval, post-larval and macrobenthic assemblages associated with kelp forests (Lessonia trabeculata) in Central Chile (30° to 33°S). Pelagic collections identified two assemblages: early-life stages and emerging macrobenthos, with the later contributing three quarters to the total abundance regardless of the source of illumination (permanent or flashing). Field experiments showed that moon phases affected the structure and composition of the samples. Surveys carried out during new moon showed the highest abundances and taxonomic richness of emergent assemblages. However, species composition varied in both assemblages depending on the moon phase. Although the pelagic assemblages collected at sites with contrasting upwelling intensity did not show differences in community structure, differences in composition were evident for early-life stages. The relationship between pelagic and benthic collections indicated that four decapod crustaceans were represented at both larval and early juvenile stages; however, only the high abundances and densities of Paraxanthus barbiger allowed for estimations of benthic-pelagic coupling. For this species, larval abundances and benthic juvenile densities demonstrated contrasting local and regional patterns, suggesting a decoupling between pelagic and benthic environments. These findings highlight the differential variability in smaller components of kelp forests, but also suggest that post-settlement processes may be driving biological interactions through these highly productive and complex environments.