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Vertical migrations of zooplankters have been widely described, but their active movements through shallow, highly dynamic water columns within the inner shelf may be more complex and difficult to characterize. In this study, invertebrate larvae, currents, and hydrographic variables were sampled at different depths during and after the presence of fronts on three different cruises off the southern coast of South Africa. Internal wave dynamics were observed in the hydrographic data set but also through satellite imagery, although strong surface convergent currents were absent and thermal stratification was weak. During the first two cruises, fronts were more conspicuous and they preceded strong onshore currents at depth which developed with the rising tide. Vertical distributions of larvae changed accordingly, with higher abundances at these deep layers once the front disappeared. The third cruise was carried out during slack tides, the front was not conspicuous, deep strong onshore currents did not occur afterward and larval distributions did not change consistently through time. Overall, the vertical distributions of many larval taxa matched the vertical profiles of shoreward currents and multivariate analyses revealed that these flows structured the larval community, which was neither influenced by temperature nor chlorophyll. Thus, the ability to regulate active vertical positioning may enhance shoreward advection and determine nearshore larval distributions. [ABSTRACT FROM AUTHOR]

Abstract: The coupling of benthic and pelagic life stages of marine invertebrates is central to understanding their population dynamics and is influenced by hydrodynamic processes at multiple spatial scales. Here we provide a regional scale study that identifies mesoscale oceanographic features linked to the distribution of mussel larvae. We surveyed the distribution of mussel larvae along 12 shelf to slope transects within an alongshore distance of about 700km along the Agulhas Bank off South Africa. Oceanographic and larval abundance data were collected simultaneously to determine how larval distribution is related to physical factors. Larval abundances were most closely correlated with temperature, salinity, beam attenuation (which indicates particle concentrations), and zonal (east–west) water velocity. In most regions, the highest larval concentrations were observed within an average distance of 3.7km from the coastline. Three mesoscale oceanographic mechanisms were identified that could explain larval distribution on separate parts of the coast. These were: a solitary meander whose leading end advects the Agulhas Current onto the continental shelf as an Agulhas Current Meander and whose lagging end advects the Agulhas Current offshore as a Natal Pulse, and the accumulation of larvae in a region with known internal wave activity. The Agulhas Current Meander swept large numbers of recently “spawned” larvae up to 30km offshore, acting as a corridor for larval loss, or a population sink. Onshore retention seems, however, to be generally characteristic of this region, when the Agulhas Current is not on the continental shelf. This study highlights how mesoscale features are associated with larval density, transport, and coupling between the pelagic and benthic systems of the Agulhas Bank. [Copyright &y& Elsevier]

Abstract: The Agulhas Current on the east coast of South Africa is a major western boundary current that exchanges heat and salt between the Indian and South Atlantic Oceans. The current retroflects as it deflects away from the African continent at the southern tip of the Agulhas Bank, a biologically productive extension of the continental shelf south of the South African coast. The less energetic Benguela Current borders the Agulhas Bank to the west. Little is known about mesoscale interactions between the Agulhas Current and the shelf waters of the Agulhas Bank or how these processes influence the biology of the bank. In this study, physical and biological data collected during a dedicated cruise in September 2010 allowed the identification of several mesoscale features that indicate a strong effect of the current on the bank, including a Natal Pulse that forced the Agulhas Current onto the Agulhas Bank. While on the bank itself, the current entrained particles that were then transported offshore. We also found evidence of upwelling on the southeast edge of the Agulhas Bank, which is thought to be a source of water for a cold ridge that characterizes the eastern region of the bank. Large fluctuations of the thermocline, consistent with internal waves, were observed inshore of the Agulhas Current, with high phytoplankton concentrations at their crests. We suggest that this is a physical effect, with doming of the waves concentrating plankton at their crests, thereby creating episodic biological hotspots. [Copyright &y& Elsevier]

Although multiple paternity and sperm storage are common in squamates, neither has been conclusively demonstrated in the chameleons (Chamaeleonidae). To examine whether these traits are present in chameleons, the Cape Dwarf Chameleon (Bradypodion pumilum) was investigated. This viviparous species inhabits a temperate climate in southern Africa, has aseasonal breeding, and can produce multiple clutches annually. Given this reproductive schedule, we hypothesised that females may mate opportunistically and store sperm, and that single clutches may have multiple sires. To examine this, six females and their clutches were genotyped using microsatellite markers, and assessed for multiple paternity. In addition, 46 females were assessed for sperm storage structures and presence of sperm in the oviduct. Multiple paternity was found in all six clutches, based on the presence of multiple alleles at all loci that could not be assigned to the mother. No evidence of specialised sperm storage structures was found, but sperm was present in the lumen of the posterior oviduct in 74% of females. While sperm storage cannot be concluded with finality, it seems likely to occur, rather assuming that three out of four of the females in the sample had mated just prior to capture. Furthermore, two post-partum females retained sperm in the oviducts after the delivery of a clutch, but in the absence of additional copulation. Given that this species has aseasonal reproduction, if sperm is indeed stored long-term, this combination of traits would be advantageous given the lack of defined breeding season and presumably low rates of mate encounter. [ABSTRACT FROM AUTHOR]