Rocky shore ecology has been studied for a long time, starting with qualitative descriptions and becoming more quantitative and experimental over time. Some of the earliest manipulative experimental ecological studies were undertaken on rocky shores. Many, over time, have made considerable contributions to ecological theory, especially highlighting the importance of biological interactions at the community level. The suitability of rocky shores as convenient test systems for ecological experimentation is outlined. Here we consider contributions from rocky shores to the emerging concepts of supply-side ecology, the roles of competition, predation and grazing, disturbance and succession and positive interactions in structuring communities along environmental gradients. We then address alternative stable states, relationships between biodiversity and ecosystem functioning, and bottom-up and top-down control of ecosystems. We briefly consider the feedback and synergies between ecological concepts and experimental work on rocky shores, whilst still emphasizing the traditional values of marine natural history upheld in JMBA since its first publication. The importance of rigorous experimental designs championed by Underwood and co-workers is emphasized. Recent progress taking advantage of new technologies and emerging approaches is considered. We illustrate how experimental studies have shown the importance of biological interactions in modulating species and assemblage-level responses to climate change and informed conservation and management of coastal ecosystems.

Daphnia longispina (O. F. Müller 1785) and Daphnia cucullata (G. O. Sars 1862), despite coexisting in similar densities in the lake, showed different demographic cycles. To search the causes of such variances between the two Daphnia, selected population parameters (density, body proportions, reproductive output) were correlated with the density of five dominant and potentially competitive species of Cladocera. The same parameters were estimated in relation to predation pressure of vertebrates (planktivorous fish) and invertebrates (Leptodora kindtii (Focke 1844)). The obtained results show that competition had no apparent impact on life-histories of Daphnia. Different strategies of the two Daphnia resulted from the uneven effect of invertebrate and vertebrate predators. D. longispina that was affected by planktivorous fish and Leptodora kindtii invested in reproduction and carried big egg-clutches. D. cucullata, which was insignificantly influenced by fish, displayed low reproductive output but changed their body proportions in the process of cyclomorphosis when occurring with L. kindtii. Other life-history trade-offs altered during the year, in accordance with the intensity of predation pressure.