Mitochondrial phylogeography of a surf clam Mactra veneriformis in the East China Sea: Genetic homogeneity across two biogeographic boundaries

Biogeographic boundaries constraining species' distributions often generate intraspecific ‘breaks’ for those species whose ranges span them—known as the ‘biogeography-phylogeography concordance’ hypothesis. The East China Sea (ECS) in the northwestern Pacific comprises two reported boundaries: the Shandong Peninsula and the Changjiang Estuary, providing an elegant setting to test the hypothesis in marine environment. Here we investigated population structure of the surf clam Mactra veneriformis (Reeve, 1854) using 235 individuals from its major distribution in the ECS, represented by mitochondrial cytochrome oxidase I sequences. A ‘star-like’ topology with shallow divergence was revealed for all haplotypes, of which the central (also assumed ancestral) one appearing in all populations. No significant genetic structure was revealed among populations, suggesting substantial genetic homogeneity across the range. Demographic expansion was revealed for individual and overall populations, and the expansion time was estimated from 23,000 years ago. These results suggested that the M. veneriformis populations originated from an ancestral panmictic population in the ECS basin, and had experienced significant population expansion since the last glacial maximum. From a mitochondrial view, the two boundaries did not act as barriers for the phylogeography of M. veneriformis.     

Mechanisms and consequences of competition between an alien mussel, Mytilus galloprovincialis, and an indigenous limpet, Scutellastra argenvillei

The influence of an alien mussel Mytilus galloprovincialis (Lamarck) on an indigenous limpet Scutellastra argenvillei (Krauss) was investigated on the west coast of South Africa by comparing four situations in which limpets occupied rock patches surrounded by mussels: (1) ‘established patches’ of high-density adult limpets; (2) ‘experimentally cleared patches’ from which mussels were manually removed; (3) ‘naturally disturbed patches’ where mussels had been eliminated by wave action; and (4) ‘half-density’ patches formed by thinning established patches. Limpets in established patches were most effective in retarding settlement and lateral invasion by mussels, but all patches shrank due to mussel encroachment. As patches shrank, limpet density fell in established and naturally disturbed patches due to emigration. Limpets living on mussel beds were small, sparse and never achieved sexual maturity; 60% shifted to rock, whereas only 7% moved from rock to mussels. The limpets showed highest fidelity to established patches (79% after 12 months) and lowest fidelity in naturally disturbed patches (20%). Thinning of established patches reduced fidelity to 26%. Mussel beds did not provide a suitable alternative substratum for S. argenvillei after they displaced the limpets from rocks. Moreover, elimination of mussels by waves failed to allow S. argenvillei to re-establish dense, adult populations resembling those prior to arrival of the mussel. Adults of S. argenvillei feed collectively by trapping kelp blades. On the topographically complex mussel beds limpets cannot feed this way. In sum, on exposed shores where M. galloprovincialis achieves maximal recruitment and growth, S. argenvillei is incapable of preventing mussel encroachment and is likely to become completely displaced. Semi-exposed shores do, however, offer a refuge preventing global extinction of the limpet.     

The influence of coastal upwelling on the functional structure of rocky intertidal communities

Summary Relationships between organisms at all trophic levels are influenced by the primary productivity of the ecosystem, and factors which enhance rates of primary production may modify trophic relationships and community structure. Nutrient enrichment of intertidal and nearshore waters leads to enhanced production by intertidal algae, and it was hypothesized that where rocky shores are washed by nutrient-rich upwelled waters, the intertidal communities should show a characteristic functional structure, based on the effects of enhanced primary production. Study sites were chosen on rocky shores in southern Africa, central Chile and the Canary Islands, in areas with and without coastal upwelling, and mid-shore community structure at these sites was analysed in terms of the abundance of certain functional guilds of organisms.It was found that algal cover and the biomass of herbivorous limpets supported per unit area on rocky shores were significantly greater in regions of coastal upwelling than in regions where upwelling did not occur. Ground cover by sessile filter-feeding organisms was significantly greater on shores in non-upwelled areas. However, correspondence analysis showed no functional aspect of intertidal community structure that was characteristic of coasts washed by upwelled waters. Primary reasons for this are probably the large variations in the nature of nutrient enrichment that accompanies upwelling, and in the nutrient status of non-upwelled areas. Other factors are man's exploitation of intertidal organisms and differences in the genetic origins of the intertidal species involved.     

The occurrence of oligochaetes in lake chains receiving pulp mill waste and their relation to eutrophication on the trophic scale

Earlier conceptions of oligochaetes as indicators of trophy were somewhat enlarged to include more littoral, meiofaunal and naidid species. The amplitudes of different species on the oligotrophy-eutrophy axis seem to be generally large. Certain species which probably originally occur mainly in very humic environments seem also to be able to endure very strong organic loading caused by pulp mills. Species of this kind seem to be Dero digitata, Specaria josinae, Slavina appendiculata and Aulodrilus pluriseta. Chaetogaster langi and Arcteonais lomondi are also species which live in areas receiving pulp mill wastes. A. lomondi and D. digitata seem to be species living in greater depths than the naidids generally. Tubifex tubifex densities as high as 600000 ind · m^-2 were found near a pulp mill when the meiofauna method was used. A third of the T. tubifex were found deeper than 5 cm from the sediment surface. S. josinae and S. appendiculata may be found down to depths between 5 and 10 cm.     

Ecosystem response to different management options in Marine Protected Areas (MPA): A case study of intertidal rocky shore communities

Marine Protected Areas (MPA) can be powerful coastal management tools with several specific goals, although there is debate concerning their effectiveness. There is no consensus regarding the ideal size of MPAs, and actually there is some evidence that perhaps size is not as critical as other specific factors in determining their success in terms of populations’ protection and ecological functions conservation. On the other hand, depending on the objectives, zones with different classification regimes in terms of rules and uses might enable the maintenance of the intended uses.At this light, we examined the case of the small (605 002 m²) rocky shore area of Avencas, near Lisbon, on the Atlantic western Coast of Portugal, which was classified as Biophysical Interest Zone (ZIBA) in 1998, due to its exceptional intertidal biodiversity, after what its protection status became controversial, leading to conflicts with the local population and incompliance with extant regulations. From 2010 efforts were carried out by local authorities to reclassify Avencas as Marine Protected Area, which was achieved in 2016.Monitoring intertidal communities in a MPA and adjacent areas is an effective and low-cost procedure to evaluate the evolution of the biodiversity of rocky shores. Therefore, antedating the creation of the new MPA, assessments of the ZIBA biodiversity were conducted from January 2013 to December 2015 on a monthly basis. This timeline was selected as a function of a change in visitors’ behavior induced from 2013 by several management and outreach initiatives, which increased in a certain extent the user’s compliance with regulations.A positive evolution was expected for density and/or species diversity of the different groups analysed (flora, sessile fauna and mobile fauna) in this three years period. However, a very strong storm occurred in 2014 produced a significant impact and changed large areas of the Avencas rocky shore. As a consequence, results did not display a recognizable recovery pattern of the intertidal communities, and following that extreme event are not even consistent with a hypothesized enhanced recovery capability of the ecosystem in a protected area. This suggests that longer data series are necessary to obtain more robust data regarding natural variability, since alterations caused by extreme events are always likely to occur. Additionally, results illustrate that indeed size matters because it influences the MPA openness, expressed as the ratio of periphery to area, and therefore its susceptibility to external driving forces. Such considerations must be taken into account in any management plan, which in this case should encompass an increase in the intertidal protected area, a new conditioned small-scale fishing regime, and an adequate monitoring programme to evaluate the effectiveness of the new management scheme.     

Response of an estuarine ecosystem to reduced organic waste discharge

Since the mid-19^th century large amounts of organic wastewere sluiced out into the Ems Estuary on the border between Germany and TheNetherlands. This waste originated from the regional potato flour and cardboardindustries making the inland waterways completely anoxic. In the estuaryseriousoxygen depletion occurred, especially during autumn. Most of the organic wasteentered the estuary in the Dollard, a brackish embayment of the Ems Estuary. Anintensive sanitation scheme was started in the 1970s, leading to a stepwisereduction of the organic waste load on the estuary. In this paper, a review isgiven of the response of the benthos living at intertidal mudflats,viz. microphytobenthos (diatoms), meiofauna (nematodes)andmacrozoobenthos. The benthos response is described mainly on the basis of dataobtained under conditions of high (ca. 1980), intermediate (1987) and largelyreduced (1993) organic waste loading.Reduction of organic loading caused significant changes in abundance, speciescomposition and standing stock of diatoms and nematodes. Macrobenthicpopulations recovered from being severely reduced regularly during the autumnalwaste discharges towards a more stable situation. Altogether, the intertidalmudflat benthos changed from organic waste loading stress towards a normal,estuarine environmental stress. This was especially the case at high and muddyflats in the southeast of the Dollard. At mixed sand/mud flats in the centre ofthe Dollard, a response of macrozoobenthos may have been obscured by theinvasion of the polychaete Marenzelleria cf.wireni.     

Responses of cyclic phosphorylation of MAPK-like proteins in intertidal macroalgae after environmental stress

The presence and activation of MAPK-like proteins in intertidal macroalgae is described in the current study. Two MAPK-like proteins of 40 and 42 kDa in size similar to p38 and JNK, of mammalian cells have been identified in six representative species of intertidal macroalgae from the Strait of Gibraltar (Southern Spain), namely in the chlorophytes Ulva rigida and Chaetomorpha aerea, the rhodophytes Corallina elongata and Jania rubens, and the phaeophytes Dictyota dichotoma and Dilophus spiralis. Phosphorylation of MAPK-like proteins was studied during semi-tidal cycles. Analysis of p38-like and JNK-like MAPKs in macroalgae protein extracts was carried out by using specific antibodies against the phosphorylated forms of both MAPKs. Protein blot analysis of samples collected from 2009 to 2011 in natural growing sites on days when either low or high tide occurred at midday, indicated that MAPK-like proteins in all species were highly phosphorylated in response to desiccation imposed by low tide or high irradiance. Phosphorylation of p38-like MAPK always preceded that of JNK-like MAPK. In addition, phosphorylation of MAPKs was fastest in rhodophytes, followed by chlorophytes and then finally phaeophytes. In the first group, phosphorylation was mostly dependent on desiccation, whereas both high irradiance and desiccation were responsible for p38-like and JNK-like phosphorylation in chlorophytes. In phaeophytes, high irradiance was mostly responsible for MAPK-like activation.     

Behavioural adaptations of the fiddler crabs Uca vocans borealis (crane) and Uca lactea lactea (De Haan) for coexistence on an intertidal shore

The distribution and coexistence of the fiddler crabs U. vocans borealis and U. lactea lactea was investigated in the upper shore of a sandy beach with respect to particle size, water content and total organic carbon content of the sediments. A clear segregation of habitats between the two species was apparent. U. lactea lactea were only found in sediments with significantly lower total organic carbon content. U. lactea lactea had a higher ratio for the size of third maxilliped to body size than U. vocans borealis. There was no statistical difference in the median sediment particle size of the habitats where both species were found on the study shore. U. lactea lactea was larger on shores where U. vocans borealis were absent. Smaller U. vocans borealis individuals occupied sediments with higher water content and finer particles. Smaller individuals of U. vocans borealis also possessed fewer spoon-tipped setae on second maxilliped than their larger conspecifics, which were found mostly on coarser sediments. U. lactea lactea spent significantly more time on the surface than in the burrow during low tide when compared with U. vocans borealis. Both Uca species exhibited similar desiccation resistance. U. lactea lactea tends to keep its frontal region in close contact with sediments to maintain moisture when being exposed to air.     

Complex and flexible life history of a freshwater benthic harpacticoid species

SUMMARY. 1. The life history of the benthic harpacticoid paracamptus schmeili (Crustacea: Copepoda) in the oligotrophic lake Pääjärvi, South Finland, was described from quantitative field data of all developmental stages. The generation time of P. schmeili was exceptionally long for a meiobenthic animal and varied with depth from 1 year in the littoral (depths of 1 and 2m) to 2 years in the upper profundal (13 and 14 m). and to 3 years in the lower profundal (40 m).
2. In the littoral, egg-bearing females were found from April to October, with peaks in spring and late summer, while in the profundal a single summer egg peak was present.
3. In the littoral and in the lower profundal there were three, in the upper profundal) probably four, simultaneous parallel cohorts over-wintering as adults, medium-sized (at 13 m also large) copepodids and medium-sized nauplii. Reproductive isolation of the parallel cohorts was possible at all depths.
4. The between-depth variation in the life history of P. schmeili was probably mainly a phenotypic response to the changing level and seasonal course of temperature and food supply. Growth and reproduction were confined to summer months, and the lengthening generation times with depth accompanied decreasing summer temperatures.
5. The cessation of growth in winter was probably due to a shortage of food, which may also have accentuated the size differences of the overwintering groups through intraspecific competition.     

Thermal biology of horseshoe crab embryos and larvae: A role for heat shock proteins

Eggs of the American horseshoe crab, Limulus polyphemus L., develop on sandy estuarine beaches during the spring and summer, and are potentially vulnerable to thermal stress during the 3-4 weeks of development to the first instar (trilobite) larval stage. In many marine taxa, heat shock (stress) proteins (Hsp's) help individuals acclimate to stresses by restoring the proper folding of cellular proteins whose shape has been altered by temperature shock or other forms of environmental stress. We examined the survival of embryos and first instar (trilobite) larvae following heat shock, and compared the levels of Hsp70 in heat shocked and control animals. Animals acclimated to 13 or 22 °C had close to 100% survival when heat shocked for 3 h at 35 or 40 °C, but exposure to 45 °C for 3 h was lethal. To study the effect of heat shock on Hsp70 production under environmentally realistic conditions, animals were acclimated to either 13 or 22 °C, heat-shocked at 35 °C for 3 h, and soluble proteins were extracted following 0, 2, 4, or 6 h recovery at 22 °C. The relative amounts of Hsp70 in horseshoe crab embryos and larvae were examined using SDS-PAGE and Western blotting. Relative to controls animals held at a constant temperature, there was a slight elevation of Hsp70 only among heat shocked trilobite larvae in the 6 h recovery treatment. Hsp70 levels did not differ significantly between control and heat shocked embryos. Horseshoe crabs have adapted to living in a thermally stressful environment by maintaining a high baseline (constitutive) level of cellular stress proteins such as Hsp70, rather than by synthesizing inducible Hsp's when stressful temperatures are encountered. This may be an effective strategy given that the heat shocks encountered by intertidal embryos and larvae occur regularly as a function of diurnal and tidal temperature changes.