Rocky shore monitoring around the Sullom Voe Oil Terminal in Shetland has produced a 20 yr dataset of population fluctuations for 40-plus species at 15 to 20 sites separated by distances up to 30 km. Synchrony in population changes was quantified by correlation among series of abundance categorised on quantitative scales. Two periods were analysed separately, pre-and post-1992, following changes in methods and extent of monitoring. Positive average correlations among sites were found for 10 out of 16 species pre-1992 and for 23 out of 26 post-1992, statistically significant for 4 and 8 species for the 2 periods, respectively. The intertidal barnacle Semibalanus balanoides showed most synchrony among sites for both periods, while dogwhelks Nucella lapillus and macroalgae (Fucus vesiculosus, F. serratus, Mastocarpus stellatus) had very low average correlations among sites. Littorina saxatilis was the only other species with significant positive correlation among sites in both periods. Corallinaceae, Verrucaria maura and V. mucosa, and Littorina neglecta were less synchronised pre-1992 than post-1992, while L. obtusata showed less synchrony post-1992. Differences in reproductive biology and ecology failed to explain patterns of synchrony among species. Species with planktonic larvae were no more likely to be synchronised than those without. There was a tendency for species living higher on the shore to be more synchronised post-1992, but species predominant on wave-exposed shores were no more synchronous than sheltered-shore species. The more synchronised species in this study need to be monitored at relatively few sites to detect change, whereas more sites may be needed for species in which change occurs on a local scale. Population synchrony also suggested usefulness of species as indicators of large-scale change: the barnacle S. balanoides is the best indicator among species in the study area.

Changes in rocky shore community composition as responses to climatic fluctuations and anthropogenic warming can be shown by changes in average species thermal affinities. In this study, we derived thermal affinities for European Atlantic rocky intertidal species by matching their known distributions to patterns in average annual sea surface temperature. Average thermal affinities (the Community Temperature Index, CTI) tracked patterns in sea surface temperature from Portugal to Norway, but CTI for communities of macroalgae and plant species changed less than those composed of animal species. This reduced response was in line with the expectation that communities with a smaller range of thermal affinities among species would change less in composition along thermal gradients and over time. Local‐scale patterns in CTI over wave exposure gradients suggested that canopy macroalgae allow species with ranges centred in cooler than local temperatures (‘cold‐affinity’) to persist in otherwise too‐warm conditions. In annual surveys of rocky shores, communities of animal species in Shetland showed a shift in dominance towards warm‐affinity species (‘thermophilization’) with local warming from 1980 to 2018 but the community of plant and macroalgal species did not. From 2002 to 2018, communities in southwest Britain showed the reverse trend in CTI: declining average thermal affinities over a period of modest temperature decline. Despite the cooling, trends in species abundance were in line with the general mechanism of direction and magnitude of long‐term trends depending on the difference between species thermal affinities and local temperatures. Cold‐affinity species increased during cooling and warm‐affinity ones decreased. The consistency of responses across different communities and with general expectations based on species thermal characteristics suggests strong predictive accuracy of responses of community composition to anthropogenic warming.

We calculated the annual production of epilimnetic crustacean zooplankton in Lake Ontario from data on the abundance of each species and its eggs, and from predictions of egg development times. Bosmina longirostris is the most productive species at the nearshore stations whereas Diacyclops thomasi is the most productive offshore. Total crustacean zooplankton production is fairly uniform throughout the lake, both nearshore and offshore, with the possible exception of somewhat reduced production at the western end of the lake. Average total production was estimated at 15 g∙m−2∙yr−1. Using a recent estimate of particle-size-conversion efficiency in Lake Ontario, obtained from data on contaminant concentrations in aquatic biota, we predicted potential fish production in the lake for various sizes of fish. From published data on the commercial fish harvest from 1910 to 1930, a time period when commercial production was at a maximum, we estimate that the past commercial harvest for pelagic species may have been 20% or more of our predicted potential production.

The long-term monitoring of two stations, 55 and 80 m depth, from 1971 to 1985 shows clear evidence of periods of stability interspersed with periods of change. These periods were identified by several different multivariate methods and persistence stability was quantified by the use of a between years similarity index. A short period of change at the shallow station, 1972–3, was followed by a prolonged period of stability 1974–80. The period 1981–3 witnessed a second period of change with rising total numbers and biomass with some evidence of a downward reversal in 1984–5. The deep station exhibited an essentially similar response except that the stable period 1974–80 was broken into two sub-periods 1974–6 and 1978–80 due to sequential changes in the dominant species which were regarded as evidence of biological interaction with the activities of the polychaete Ophelina acuminata possibly playing a key role. The shallow station showed little evidence of biological interaction and the majority of the species have exhibited similar responses throughout. The general rise in numbers and biomass at both stations is regarded as evidence of intermittent changes in organic flux to the bottom from the water column. The winter temperature fluctuations were shown to have short-term, but significant, effects on the diversity of the communities, bringing about year to year changes in the equitability and dominance.

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