Oceanographic and behavioural processes affecting invertebrate larval dispersal and supply in the western Iberia upwelling ecosystem

Abstract

The present review addresses recent findings made in the western Iberia ecosystem on the behavioural and physical interactions that regulate dispersal, supply to coastal habitats and settlement of invertebrate larvae. These studies used the barnacle Chthamalus spp. and the crab Carcinus maenas as model organisms. The observations made on the Iberian shelf showed extensive diel vertical migrations along the water column by representatives of both groups that have never been reported before. The interaction of the diel vertical migration with the two-layer flow structure of upwelling/downwelling circulation suggests a mechanism that may help to retain larvae in shelf waters during upwelling conditions. Measurements of daily supply of C. maenas megalopae to estuaries separated by 500 km disclosed a semilunar pattern, with highest supply around highest amplitude tides, indicating that supply of megalopae to estuaries is accomplished by selective tidal stream transport. Relaxation of equatorward winds also played a role in supply, by enhancing translocation of megalopae to the nearshore. Concerning Chthamalus larvae, the observations on daily settlement made at rocky shores also separated by 500 km showed unclear patterns between locations and years. The relationship of settlement with water temperature, tidal range and upwelling indices indicated that supply of barnacle cyprids may be controlled by multiple mechanisms, viz. upwelling/downwelling circulation, internal tidal bores and sea breezes.

Shelf and estuarine transport mechanisms affecting the supply of competent larvae in a suite of brachyuran crabs with different life histories

“…1988. Understanding the mechanisms responsible for larval delivery to the parental habitat, and identifying the connectivity pathways that make sink populations viable are important tasks for the conservation of littoral marine resources.Larval transport is mainly explained by the physical forcing of winds and tides because larval swimming is usually insufficient to countervail current speeds usually observed in the ocean and nearshore waters (Shanks 2006, Queiroga et al 2007). In upwellingdominated coastlines, many studies have provided evidence of large-scale Ekman transport caused by longshore wind stress, mostly after the pioneering work of Roughgarden et al (1988).…”

Barnacle larval transport in the Mandovi–Zuari estuarine system, central west coast of India

“…Recruitment may be broadly defined as the replenishment of a population with new individuals due to the process of reproduction and growth. For marine species with indirect development, recruitment involves several steps: larval development, dispersal during development, supply to appropriate settlement habitats, settlement and juvenile development (Queiroga et al 2007). The model results indicate that the presence of barnacle larvae in the estuary is more or less controlled by spawning sites in the outer estuarine areas, as there is a clear presence of larvae coming from other sites and settling in the estuary.…”

“…Barnacles form large populations of adults on rocky shores and in estuaries which have the capacity to strongly affect the community structure through spatial interference completion (Hughes and Griffiths 1988;Wootton 1993;Queiroga et al 2007). Recruitment may be broadly defined as the replenishment of a population with new individuals due to the process of reproduction and growth.…”

“…The currently accepted view is that invertebrate and fish larvae migrate into estuaries using selective tidal stream transport (Forward and Tankersley 2001). During upstream selective tidal stream transport, larvae settle on or move close to the bottom during ebb tides to avoid being displaced seaward or ascend in the water column during flood tides (Queiroga et al 2007). …”

Seasonal cycle of plankton production in the Iberian margin based on a high resolution ocean model

“…Castro et al, 2000;Cravo et al, 2010;Queiroga et al, 2007;Santos et al, 2007). For example, the shelf--ocean exchange of biogenic materials is thought to be strongly influenced by such mesoscale events, the off-shelf export being favored through filaments developed during the spring--summer upwelling (Álvarez-Salgado et al, 2001(Álvarez-Salgado et al, , 2007Cravo et al, 2010) in opposition to in situ mineralization favored by autumn--winter termohaline fronts developed under downwelling conditions/slope poleward flow (Álvarez-Salgado et al, 2003).…”