The marine and coastal access act—A hornets' nest?

The Marine and Coastal Access Act 2009 is now enacted into law. This paper looks at predictions made about new law by one of the authors, Peter Jones, in his paper The Marine Bill: Cornucopia or Pandora's Box [1] and assesses how successful the Act has been in turning aspirations into law. The paper focuses on the following areas: ecosystem protection, stakeholder engagement, marine spatial planning and the provision of a network of highly protected marine reserves, and raises concerns that the ecosystem approach has progressively been dropped in the drafting process of the legislation. Concerns are raised that the new Inshore Fisheries and Conservation Authorities have similar inherent conflicts of interest to those exhibited by Sea Fisheries Committees, which they sought to replace. The effectiveness of marine planning is questioned, as there appear to be inbuilt loopholes for public authorities to avoid complying with the marine plans. The draft marine policy statement (MPS), published in July 2010, includes appropriate environmental safeguards, but the MPS has not yet been formally adopted. The absence of a concrete target for highly protected marine reserves means there is a danger that designations under the Act may have little effect on the ground. In conclusion the Act provides some new mechanisms for marine protection, but arguably does not yet provide a framework for implementing the ecosystem approach and is not an end in itself.     

In situ tensile fracture toughness of surficial cohesive marine sediments

This study reports the first in situ measurements of tensile fracture toughness, K _IC, of soft, surficial, cohesive marine sediments. A newly developed probe continuously measures the stress required to cause tensile failure in sediments to depths of up to 1 m. Probe measurements are in agreement with standard laboratory methods of K _IC measurements in both potter’s clay and natural sediments. The data comprise in situ depth profiles from three field sites in Nova Scotia, Canada. Measured K _IC at two muddy sites (median grain size of 23–50 μm) range from near zero at the sediment surface to >1,800 Pa m^1/2 at 0.2 m depth. These profiles also appear to identify the bioturbated/mixed depth. K _IC for a sandy site (>90% sand) is an order of magnitude lower than for the muddy sediments, and reflects the lack of cohesion/adhesion. A comparison of K _IC, median grain size, and porosity in muddy sediments indicates that consolidation increases fracture strength, whereas inclusion of sand causes weakening; thus, sand-bearing layers can be easily identified in K _IC profiles. K _IC and vane-measured shear strength correlate strongly, which suggests that the vane measurements should perhaps be interpreted as shear fracture toughness, rather than shear strength. Comparison of in situ probe-measured values with K _IC of soils and gelatin shows that sediments have a K _IC range intermediate between denser compacted soils and softer, elastic gelatin.     

Regarding an Oceanic Crust/Upper Mantle Geochemical Signature at the KT Boundary: If not from Chicxulub Crater, then Where Did it Come from?

Evidence for a mantle and/or basaltic component in KT boundary distal ejecta is apparently inconsistent with ejection from Chicxulub Crater since it is located on~35km thick continental crust(De Paolo et al.,1983;Montanari et al.,1983;Hildebrand and Boynton,1988,1990).This evidence,along with ejected terrestrial chromites(Olds et al.,2016)suggest the impact sampled terrestrial mafic and/or ultramafic target rocks which are not known to exist in the Chicxulub target area.Possible resolutions to the paradox are:1)the existence of an unmapped/unknown suture in Yucatan Platform basement,2)an additional small unmapped/unknown impact site on oceanic lithosphere,or 3)an additional large impact on oceanic lithosphere or continental margin transitional to oceanic lithosphere.The third hypothesis is elaborated here since:1)Ophiolites nearest to Chicxulub crater are found in Cuba and apparently were obducted in latest Cretaceous/earliest Danian times(García-Casco,2008),inconsistent with the documented Eocene collision of Cuba with the Bahamas platform;and 2)Cuba hosts the world’s thickest known KT boundary deposits(Iturralde-Vinent,1992;Kiyokawa et al.,2002;Tada et al.,2003).These and geometric considerations suggest oceanic crust and upper mantle rock,exposed as ophiolite in the Greater Antilles island chain,marks the rim of a roughly 700 km diameter impact basin deformed and dismembered from an originally circular form by at least 50 million years of left-lateral shear displacement along the North American-Caribbeantransform plate boundary.     

Comparison of surface and borehole locations of induced seismicity

Monitoring of induced microseismic events has become an important tool in hydraulic fracture diagnostics and understanding fractured reservoirs in general. We compare microseismic event and their uncertainties using data sets obtained with surface and downhole arrays of receivers. We first model the uncertainties to understand the effect of different acquisition geometries on location accuracy. For a vertical array of receivers in a single monitoring borehole, we find that the largest part of the final location uncertainty is related to estimation of the backazimuth. This is followed by uncertainty in the vertical position and radial distance from the receivers. For surface monitoring, the largest uncertainty lies in the vertical position due to the use of only a single phase (usually P‐wave) in the estimation of the event location. In surface monitoring results, lateral positions are estimated robustly and are not sensitive to the velocity model. In this case study, we compare event location solutions from two catalogues of microseismic events; one from a downhole array and the second from a surface array of 1C geophone. Our results show that origin time can be reliably used to find matching events between the downhole and surface catalogues. The locations of the corresponding events display a systematic shift consistent with a poorly calibrated velocity model for downhole dataset. For this case study, locations derived from surface monitoring have less scatter in both vertical and horizontal directions.     

Evaluating MT3DMS for Heat Transport Simulation of Closed Geothermal Systems

Owing to the mathematical similarities between heat and mass transport, the multi-species transport model MT3DMS should be able to simulate heat transport if the effects of buoyancy and changes in viscosity are small. Although in several studies solute models have been successfully applied to simulate heat transport, these studies failed to provide any rigorous test of this approach. In the current study, we carefully evaluate simulations of a single borehole ground source heat pump (GSHP) system in three scenarios: a pure conduction situation, an intermediate case, and a convection-dominated case. Two evaluation approaches are employed: first, MT3DMS heat transport results are compared with analytical solutions. Second, simulations by MT3DMS, which is finite difference, are compared with those by the finite element code FEFLOW and the finite difference code SEAWAT. Both FEFLOW and SEAWAT are designed to simulate heat flow. For each comparison, the computed results are examined based on residual errors. MT3DMS and the analytical solutions compare satisfactorily. MT3DMS and SEAWAT results show very good agreement for all cases. MT3DMS and FEFLOW two-dimensional (2D) and three-dimensional (3D) results show good to very good agreement, except that in 3D there is somewhat deteriorated agreement close to the heat source where the difference in numerical methods is thought to influence the solution. The results suggest that MT3DMS can be successfully applied to simulate GSHP systems, and likely other systems with similar temperature ranges and gradients in saturated porous media.     

Recurrence of the world’s largest green-tide in 2009 in Yellow Sea, China: Porphyra yezoensis aquaculture rafts confirmed as nursery for macroalgal blooms

In the summer of 2008, the world’s largest green-tide occurred in the Yellow Sea, China. The hypothesized cause was the expansion of Porphyra yezoensis aquaculture along the Jiangsu coastline and the re-occurrence of a green-tide in 2009 was predicted. In this study, satellite and field images showed the formation of the June 2009 green-tide which again originated from the Jiangsu coast. The responsible species, its source and biomass accumulation were studied to support the previous hypothesis. Morphological and phylogenetic analysis demonstrated the homology of Ulva prolifera in the 2008 green-tide with the U. prolifera from P. yezoensis aquaculture rafts. About 91-505 kg/ha of U. prolifera was attached to the P. yezoensis aquaculture rafts and a total biomass of 4956 tonnes was estimated during the harvesting of P. yezoensis. This is sufficient to seed a bloom when they are dislodged from the rafts as a result of harvesting practices.