Consumer

Abstract: 1. The Estuarine Environment 2. Life in Estuaries 3. Primary Producers: plant production and its availability 4. Primary Consumers: herbivores and detritivores 5. The Secondary Consumers: carnivores 6. Estuarine Uses and Users 7. Methods for Studying Human-Induced Changes in Estuaries 8. The Management of Estuaries

Abstract: 1 The Estuarine Environment.- 1.1 Introduction.- 1.2 Estuarine circulation.- 1.3 Estuarine sediments.- 1.4 Other physico-chemical factors.- 1.5 Distribution of estuarine organisms.- 1.6 The problems of life in estuaries.- 1.7 The estuarine food web.- 2 Primary Producers Plant production and its availability.- 2.1 Introduction.- 2.2 Salt marshes.- 2.3 Intertidal plants.- 2.4 Phytoplankton.- 2.5 Detritus.- 2.6 Summation of plant and microbial production in estuaries.- 3 Primary Consumers Herbivores and detritivores.- 3.1 Introduction.- 3.2 The mud dwellers.- 3.3 The surface dwellers.- 3.4 Meiofauna.- 3.5 Zooplankton.- 3.6 The primary consumer community.- 4 The Secondary Consumers Carnivores.- 4.1 Introduction.- 4.2 Fish.- 4.3 Invertebrates.- 4.4 Birds.- 4.5 The impact of the secondary consumers.- 5 Estuarine Pollution.- 5.1 Introduction.- 5.2 Mankind's use of estuaries.- 5.3 Methodologies of studying pollution.- 5.4 Organic enrichment.- 5.5 Industrial contamination.- 5.6 Reclamation and engineering works.- 6 The Management of Estuaries.- 6.1 Introduction.- 6.2 Policies.- 6.3 Planning.- 6.4 Practice.- Reading List.

Abstract: Lake Victoria's fish fauna included a large endemic flock of 300+ haplochromine cichlid species. About two-thirds of these species have disappeared or are threatened with extinction. The main cause of this large extinction event is predation by Nile perch, an introduced predator. We describe the decline of the haplochromine species and demonstrate that the rate and sequence of their decline was determined by their relative abundance, their adult size and their habitat overlap with Nile perch. Many non-haplochromine species declined as well, but in contrast, stocks of the native pelagic cyprinid Rastrineobola argentea and the introduced Oreochromis niloticus increased. There are also indications of an increase in phytoplankton, macrophytes, prawns and benthic organisms. Many of these rapid changes in the ecosystem were probably effects of the increase of the Nile perch and the disappearance of the haplochromines. The original fish fauna included many primary and secondary consumers. Currently secondary and tertiary consumers dominate. The food web in the sub-littoral and offshore areas of the lake changed considerably due to the stock replacements.

Abstract: The global nitrogen cycle has been greatly perturbed by human activities resulting in elevated nitrogen deposition in many parts of the world. The threat nitrogen deposition poses to ecosystem function and biodiversity is increasingly recognised. In terrestrial systems, impacts on the plant community are mainly through eutrophication and soil acidification. Interactions with secondary environmental drivers such as extreme weather and disease are also key mechanisms. Impacts on consumers can be caused by changes in the quality or quantity of food as a result of changes in food plant chemistry or species composition, changes in vegetation structure leading to a change in the availability of prey species, nesting sites or cooled microclimates or changes in the phenology of plants leading to causing phenological asynchrony. Primary consumers have received considerably less research attention than plants but negative impacts have been observed for both folivorous insects and pollinators. Mammal herbivores have received little research attention. New analysis of changes in plant traits along a gradient of nitrogen deposition in the UK shows that plants pollinated by large bees were negatively associated with N deposition whilst low pH was associated with lower nectar production, reduced occurrence of plants pollinated by long‐tongued insects and a reduction in plants with larger floral units. Very few studies have investigated the effects on secondary consumers, but those that have suggest that there are likely to be negative impacts. This review identifies considerable knowledge gaps in the impacts of N deposition on higher tropic levels and highlights that for many groups, knowledge of N deposition impacts is patchy at best. Evidence that has been collected suggests that there are likely to be impacts on primary and secondary consumers making this a priority area for investigation.