Contribution of photosynthetic gains during tidal emersion to production of Zostera capricorni in a North Island,New Zealand estuary

Photosynthetic characteristics of intertidal Zostera capricorni were measured under different tidal conditions in Whangapoua Harbour on the eastern Coromandel Peninsula, New Zealand, and compared with permanently submerged seagrass beds. Photosynthetic characteristics were measured using pulse amplitude modulated (PAM) fluorom‐etry and oxygen (O2) electrode techniques. Gross light saturated photosynthesis measured as oxygen exchange averaged 5.74 and 5.36 mg O₂ g^–1 dry weight (DW) h^–1 and leaf respiration rates averaged 1.22 and 1.38 mg O₂ g^–1 DW h^–1, for intertidal and subtidal plants respectively. Photosynthesis of both intertidal and shallow subtidal plants was light saturated at between 195 and 242 μmol photons m ^–2 s^–1, suggestive of acclimation to a high light environment. Despite the period of exposure at low tide clearly being an important time for photosynthetic gains for intertidal plants, when water clarity was sufficiently high, maximum rates of photosynthesis were also possible when the beds were submerged. If average water clarity was at the clearer end of a range measured for this site (K_d = 0.85 m^–1) then it was calculated that for intertidal seagrass beds growing at mean sea level in Whangapoua, c. 50% of above‐ground production could occur while plants were submerged.     

Reduced survivorship of Himasthla (Trematoda, Digenea)-infected cockles (Cerastoderma edule) exposed to oxygen depletion

Bivalve populations from inshore waters often accommodate a diverse trematode fauna that may have a variety of effects on host specimens. In particular, larval trematodes that grow or reproduce within their host are known to be severe pathogens, whereas trematodes utilising bivalves only for encystment are thought to be relatively benign. Yet this may depend on the environmental conditions, and it can be expected that such trematodes in concert with other stress agents can be detrimental to host organisms. To examine the impact of such larval trematodes on hosts subjected to stress, we studied the digenetic trematode Himasthla elongata and one of its second intermediate hosts, the bivalve Cerastoderma edule. Experimentally infected cockles and non-infected cockles were exposed to oxygen depletion, whereupon we measured their burrowing ability and survivorship. After 30 h of hypoxia, the survival of infected cockles was significantly reduced compared to non-infected cockles, whereas no effect of parasites on cockles under normoxic conditions was found. In addition, parasites tended to reduce the burrowing ability of cockles exposed to hypoxia but the effect was not clear. The effect of parasites and possible ecological consequences are discussed and it is suggested that the combined effects of parasites and oxygen deficiency may explain some hitherto unexplained cases of mass mortalities in bivalve populations.     

Stratigraphic evolution of a submarine channel-lobe complex system in a narrow fairway within the Magallanes foreland basin, Cerro Toro Formation, southern Chile

This study integrates newly acquired stratigraphic data, geologic mapping, and paleocurrent data to constrain the stratigraphic evolution of the oldest channel-lobe complex in the Upper Cretaceous Cerro Toro Formation in the Silla Syncline area of the Magallanes Basin, termed the Pehoe member. The Pehoe member ranges in thickness from 60 m in the north to at least 410 m farther down system and comprises three separate divisions (A, B, and C). A lower conglomerate unit and an upper one, termed Pehoe A and C divisions respectively, represent the fill of major incised submarine channels or channel complexes. These are separated by stratified sandstone of the Pehoe B division, representing a weakly confined lobe complex, either transient or terminal.The integration of new data with observations from previous studies reveal that the three main coarse-grained conglomerate and sandstone members in the Cerro Toro Formation in the Silla Syncline include at least seven distinct submarine channels or channel complexes and two major lobe complexes. The thinning and disappearance of these units along the eastern limb of the syncline reflect confinement of the flows to a narrow trough or mini-basin bounded to the east by a topographic high. This confinement resulted in unidirectional paleocurrents to the south and southeast in all deposits. Changes in depositional geometries are interpreted as reflecting changes in sediment supply and relative confinement. Submarine channels were from 700 m to 3.5 km wide and occupied a fairway that was 4-5 km wide. Flows moving south and southeast in this mini-basin probably crossed the eastern topographic high south of the present exposures and joined those moving southward along the axis of the foreland basin at least 16 km to the east.     

Where could catch shares prevent stock collapse?

In a widely received study Costello and his colleagues found that catch shares give better stock persistence and higher catch for fishermen. The conclusions made by Costello et al. were further supported by Grafton and McIlgorm where they suggested a framework in order to determine the costs and benefits of separate ITQ management in seven Australian commonwealth fisheries, and what the alternatives should be if the net benefits do not justify ITQs. This raises the question why we do not see catch shares being used more often. We explore at a global scale which countries would have the potential to, and indeed do, fulfil the conditions necessary to implement such a management strategy.     

Spatial mining of migration patterns from web demographics

Volunteered Geographic Information, social media, and data from Information and Communication Technology are emerging sources of big data that contribute to the development and understanding of the spatiotemporal distribution of human population. However, the inherent anonymity of these crowd-sourced or crowd-harvested data sources lack the socioeconomic and demographic attributes to examine and explain human mobility and spatiotemporal patterns. In this paper, we investigate an Internet-based demographic data source, personal microdata databases publicly accessible on the World Wide Web (hereafter web demographics), as potential sources of aspatial and spatiotemporal information regarding the landscape of human dynamics. The objectives of this paper are twofold: (1) to develop an analytical framework to identify mobile population from web demographics as an individual-level residential history data, and (2) to explore their geographic and demographic patterns of migration. Using web demographics of Vietnamese–Americans in Texas collected in 2010 as a case study, this paper (1) addresses entity resolution and identifies mobile population through the application of a Cost-Sensitive Alternative Decision Tree (CS-ADT) algorithm, (2) investigates migration pathways and clusters to include both short- and long-distance patterns, and (3) analyze the demographic characteristics of mobile population and the functional relationship with travel distance. By linking the physical space at the individual level, this unique methodology attempts to enhance the understanding of human movement at multiple spatial scales.     

Individual Variation in the Covering Behaviour of the Shallow Water Sea Urchin Paracentrotus lividus

Abstract. A number of recent field‐based studies have investigated the possible functions of covering behaviour in a range of echinoid species. Some of these have found important relationships between covering behaviour and environmental factors, such as light (in particular, ultra‐violet light) and covering item availability. However, these studies have often shown considerable within‐species variation, thus making covering functionality both within and between species difficult to interpret. The present study experimentally investigates individual variability in covering behaviour characteristics of the sea urchin Paracentrotus lividus (Lamarck). Data were collected bimonthly over a 1‐year period at Lough Hyne, Ireland, by observing P. lividus in outdoor aquaria. Significant variations in covering behaviour characteristics were observed as a function of individual size and mobility but not as a function of sex. A significant relationship between water temperature, mobility and covering behaviour was also found and is hypothesized to have implications for grazing activity in P. lividus. In contrast to previous field studies of P. lividus at Lough Hyne, no summer ‘peak’ in the proportion of individuals covering was observed. However, there was a significant relationship between local solar radiation and ‘time to first cover’. Overall, these data highlight (i) the ecological significance of individual variation in P. lividus covering behaviour and (ii) the importance of investigating multiple factors as potential determinants of echinoid covering behaviour.     

Be exposure ages of a rock avalanche and a late glacial moraine in Alta Valtellina, Italian Alps

A rock avalanche deposit was investigated in order to understand the chronological evolution of geological hazards and to evaluate the interaction of the triggering geodynamic processes in the valley Val Viola, Italian Alps. The deposit is situated west of the Alpe Dosdé, in a permafrost area with deep-seated gravitational deformations (DSGD) along a tectonic line. Based on its geomorphologic context, the rock avalanche was first interpreted as a result of slope stress release without exact timing. This hypothesis was tested by measuring the ¹⁰Be exposure date of quartz from one boulder from the rock avalanche. The age of 7430±460 years places the event in the early Holocene. The timing of the last deglaciation was constrained using the inner late glacial moraine of a moraine doublet in the valley Alpe Dosdé situated at an altitude between 2140 and 2120 m a.s.l. west of the rock avalanche. The ¹⁰Be concentrations of quartz yield minimum exposure ages of 11,480±670 and 10,850±820 years. Different proposals for potential triggering factors of the rock avalanche include (a) melting of the local valley glacier and slope stress release in the Val Viola, likely to play a minor role as trigger, because of the time delay between the deglaciation and the rock avalanche event. More likely are (b) enhanced crustal seismicity induced by post-glacial regional isostatic glacial rebound coupled with tectonic stress or/and (c) climate conditions with higher temperatures around 7430±460 years, resulting in an upwards movement of the permafrost limit and destabilization of the rock walls.