Situation of integrated coastal zone management in Central America: Experiences of the IUCN wetlands and coastal zone conservation program

Central American coastal zones possess extensive scenic and geographical wealth as well as great biological diversity. These coasts maintain 21.6% of the region’s population and produce at least US$ 750 million alone in fishing activities that provide work and sustenance for more than 450 000 persons in the region. Eight percent of the world’s mangroves are located in Central America, as well as the second largest corral reef barrier on the planet. A good representation of the region’s natural heritage is conserved in approximately 110 protected areas. Due to these special conditions, at least 50% of Central America’s coastal zones is devoted to tourism, one of the three primary economic activities in four of the region’s countries. Integrated coastal zone management (ICZM) in this region has been limited by information gaps, restricted technical and financial capacity, and strong sectoralism. Some recent projects, both governmental and supported by NGOs, offer new experience and lessons on regional ICZM. These initiatives have been backed at the ministerial and presidential level by a large number of political agreements within the framework of the ‘alliance for sustainable development’ (ALIDES).     

Year-long float trajectories in the Labrador Sea Water of the eastern North Atlantic Ocean

Year-long Lagrangian trajectories within the Labrador Sea Water of the eastern North Atlantic Ocean are analysed for basic flow statistics. Root-mean-square velocities at 1750 m depth are about 2 cm/s, except within the North Atlantic Current, where they are twice as large. These values are consistent with previous Eulerian measurements and extend those results to a much larger domain of the eastern basin. Mean flow estimates in boxes large enough to contain about 1 float-year of data indicate that Labrador Sea Water, having crossed the Mid- Atlantic Ridge (not resolved) near 50–55^°N, presumably with the North Atlantic Current, partially recirculates to the north in the subpolar gyre, as well as entering the subtropical gyre and continuing south and west. The circulation of this water mass, as defined by the 1 yr average velocities, is stronger than traditional models of deep circulation would suggest, with an interior flow of roughly 1 cm/s. Mean speeds up to 3 cm/s were observed, with the highest values near the Azores Plateau. North of 45°N–55°N, mean eastward speeds closer to 0.2 cm/s were observed. Wind-generated barotropic fluctuations may be responsible for some part of the transport at this depth.     

Very large subaqueous sand dunes on the upper continental slope in the South China Sea generated by episodic,shoaling deep-water internal solitary waves

Very large subaqueous sand dunes were discovered on the upper continental slope of the northern South China Sea. The dunes were observed along a single 40 km long transect southeast of 21.93°N, 117.53°E on the upper continental slope in water depths of 160 m to 600 m. The sand dunes are composed of fine to medium sand, with amplitudes exceeding 16 m and crest-to-crest wavelengths exceeding 350 m. The dunes' apparent formation mechanism is the world's largest observed internal solitary waves which generate from tidal forcing on the Luzon Ridge on the east side of the South China Sea, propagate west across the deep basin with amplitudes regularly exceeding 100 m, and dissipate extremely large amounts of energy via turbulent interaction with the continental slope, suspending and redistributing the bottom sediment. While subaqueous dunes are found in many locations throughout the world's oceans and coastal zones, these particular dunes appear to be unique for two principal reasons: their location on the upper continental slope (away from the influence of shallow-water tidal forcing, deep basin bottom currents and topographically-amplified canyon flows), and their distinctive formation mechanism (approximately 60 episodic, extremely energetic, large amplitude events each lunar cycle).     

Observations on the Rim Current structure,CIW formation and transport in the western Black Sea

CTD and ADCP measurements together with a sequence of satellite images indicate pronounced current meandering and eddy activity in the western Black Sea during April 1993. The Rim Current is identified as a well-defined meandering jet stream confined over the steepest topographic slope and associated cyclonic–anticyclonic eddy pairs located on both its sides. It has a form of highly energetic and unstable flow system, which, as it propagates cyclonically along the periphery of the basin, is modified in character. It possesses a two-layer vertical structure with uniform upper layer speed in excess of 50 cm/s (maximum value ∼100 cm/s), followed by a relatively sharp change across the pycnocline (between 100 and 200 m) and the uniform sub-pycnocline currents of 20 cm/s (maximum value ∼40 cm/s) observed up to the depth of ∼350 dbar, being the approximate limit of ADCP measurements. The cross-stream velocity structure exhibits a narrow core region (∼30 km), flanked by a narrow zone of anticyclonic shear on its coastal side and a broader region of cyclonic shear on its offshore side. The northwestern shelf circulation is generally decoupled from the influence of the basinwide circulation and is characterized by much weaker currents, less than 10 cm/s. The southward coastal flow associated with the Danube and Dinepr Rivers is weak during the measurement period and is restricted to a very narrow coastal zone.The data suggest the presence of temperature-induced overturning prior to the measurements, and subsequent formation of the Cold Intermediate Water mass (CIW) within the Northwestern Shelf (NWS) and interior of the western basin. The newly formed shelf CIW is transported in part along the shelf by the coastal current system, and in part it flows downslope across the shelf and intrudes into the Rim Current convergence zone. A major part of the cold water mass, however, seems to be trapped within the northwestern shelf. The CIW mass, injected into the Rim Current zone from the shelf and the interior region, is then circulated around the basin.     

我国海岸带综合管理制度、实践及存在问题

海岸带综合管理作为沿海区域实现可持续发展目标的重要途径,对沿海地区科学有效地利用海岸带资源具有重要意义。本文从国家、省、市三个层面分析了我国当前海岸带综合管理制度现状和实践状况,提出了在海岸带综合管理立法缺失、权属不清、海陆统筹不能兼顾、海岸带规划与评价不足、管理技术亟待升级、海岸带基础数据尚不完备等制度方面存在的问题;基于国内外对海岸带综合管理的经验和实践,从加快海岸带立法、完善海岸带规划、协调综合管理、兼顾陆海统筹、提升管理技术、加强管理效果评价以及夯实基础信息等方面提出海岸带综合管理制度进一步完善的措施和建议,为进一步提升我国海岸带综合管理工作提供参考。     

Scientific research in the Tamaulipas Coastal Zone,Mexico:: implications for its coastal management

The perspectives of an efficient coastal management organization for the Tamaulipas Coastal Zone in Mexico are analyzed. With seven coastal municipalities, Tamaulipas has nevertheless 430 km of littoral and the largest estuarine area in the country (231,200 ha). The main activities there are: cattle breeding, fisheries and local manufacturing and urban development is actively increasing, concentrating in the Tampico-Ciudad Madero “Metropolis.” All of this affects significantly the many important natural ecosystems present. Following a comprehensive literature search and field visits to the area, it was made clear that the State's coastal zone is largely unknown scientifically. The organization of the Country Administration for its management of natural resources is overviewed and the criteria for the selection of the nine areas considered prioritary for ecological protection or conservation are explained. The main challenges facing the area with respect to an efficient coastal management are: (1) to close the gap in its scientific knowledge and make available all existing and future information to interested parties, (2) to modify the Administration organization to make the application of legal tools more efficient (3) to encourage open discussion, exchange of ideas and interactive forums among the different sectors (scientific, administrative, public and private organizations).     

Picophytoplankton dynamics and production in the Arabian Sea during the 1995 Southwest Monsoon

Phytoplankton community structure is expected to shift to larger cells (e.g., diatoms) with monsoonal forcing in the Arabian Sea, but recent studies suggest that small primary producers remain active and important, even in areas strongly influenced by coastal upwelling. To better understand the role of smaller phytoplankton in such systems, we investigated growth and grazing rates of picophytoplankton populations and their contributions to phytoplankton community biomass and primary productivity during the 1995 Southwest Monsoon (August–September). Environmental conditions at six study stations varied broadly from open-ocean oligotrophic to coastal eutrophic, with mixed-layer nitrate and chlorophyll concentrations ranging from 0.01 to 11.5 μM NO₃ and 0.16 to 1.5 μg Chl a. Picophytoplankton comprised up to 92% of phytoplankton carbon at the oceanic stations, 35% in the diatom-dominated coastal zone, and 26% in a declining Phaeocystis bloom. Concurrent in situ dilution and ¹⁴C-uptake experiments gave comparable ranges of community growth rates (0.53–1.05 d⁻¹ and 0.44–1.17 d⁻¹, to the 1% light level), but uncertainties in C:Chl a confounded agreement at individual stations. Microzooplankton grazing utilized 81% of community phytoplankton growth at the oligotrophic stations and 54% at high-nutrient coastal stations. Prochlorococcus (PRO) was present at two oligotrophic stations, where its maximum growth approached 1.4 d⁻¹ (two doublings per day) and depth-integrated growth varied from 0.2 to 0.8 d⁻¹. Synechococcus (SYN) growth ranged from 0.5 to 1.1 d⁻¹ at offshore stations and 0.6 to 0.7 d⁻¹ at coastal sites. Except for the most oligotrophic stations, growth rates of picoeukaryotic algae (PEUK) exceeded PRO and SYN, reaching 1.3 d⁻¹ offshore and decreasing to 0.8 d⁻¹ at the most coastal station. Microzooplankton grazing impact averaged 90, 70, and 86% of growth for PRO, SYN, and PEUK, respectively. Picoplankton as a group accounted for 64% of estimated gross carbon production for all stations, and 50% at high-nutrient, upwelling stations. Prokaryotes (PRO and SYN) contributed disproportionately to production relative to biomass at the most oligotrophic station, while PEUK were more important at the coastal stations. Even during intense monsoonal forcing in the Arabian Sea, picoeukaryotic algae appear to account for a large portion of primary production in the coastal upwelling regions, supporting an active community of protistan grazers and a high rate of carbon cycling in these areas.     

Surface currents derived from satellite-tracked buoys off Namibia

To study the flow field off Namibia (20–30°S, 10–15°E), 48 satellite-tracked buoys were deployed and tracked in six bimonthly batches between July 1994 to September 1995. In situ supporting wind information was collected from a weather buoy moored off Lüderitz, from coastal stations and from voluntary observing ships. Buoy drift tracks were compared with surface topography data from the TOPEX/POSEIDON satellite and satellite infrared images. Most of the buoys drifted in a northwesterly direction, the buoys deployed in the south generally moving faster and diverging more from the coast than the northern buoys. The overall maximum daily drift velocity was 72 cm s^-1, but typical speeds were 10–30 cm s^-1. In the proximity of the coast some buoys experienced transient southward sets associated with the effect of coastal trapped waves, while tracks north of 23°S showed inertial oscillations.     

Distributions and fluxes of methyl chloride and methyl bromide in the East China Sea and the Southern Yellow Sea in autumn

We determined the distributions and fluxes of methyl chloride and methyl bromide in the East China Sea (ECS) and the Southern Yellow Sea (SYS) in November 2007. Methyl chloride and methyl bromide concentrations in the surface waters ranged from 47.1 to 163 pmol L^?1 and from 0.70 to 9.82 pmol L^? 1, with average values of 87.6 and 2.97 pmol L^? 1, respectively. The distributions of the two methyl halides were clearly influenced by the Yangtze (Changjiang) River effluent and Kuroshio water, with high concentrations appearing in the coastal zone and low values occurring in the open waters. A positive linear correlation was observed between methyl chloride and methyl bromide concentration anomalies in the surface waters, suggesting that they may share some origins in this coastal area. However, no correlation was found between the two methyl halide concentration anomalies and chlorophyll a in the surface waters. The vertical profiles of the two methyl halides were characterized by the maxima in the upper mixed layer. Both gases were generally supersaturated in the surface seawater, with mean sea-to-air fluxes of methyl chloride and methyl bromide of 391 and 20.0 nmol m^?2 d^? 1, respectively.     

Shortcomings in the European principles of Integrated Coastal Zone Management (ICZM): Assessing the implications for locally orientated coastal management using Biome Portfolio Analysis (BPA)

EU policy geared towards the sustainable development of European coastal areas has incorporated Integrated Coastal Zone Management (ICZM) as one of its primary mechanisms to achieve its goal. However, critical shortcomings in the ICZM paradigm have emerged. In particular, incoherence in the European Commission's ICZM principles with respect to local and strategic objectives remains an issue. Additionally, a lack of scientific certainty about environmental processes when determining the environmental pros and cons of alternative coastal-management decisions undermines environmentally protective decisions that may otherwise hinder local regional development. With these issues in mind, a Biodiversity Portfolio Analysis (BPA) is applied to Iarras Aithneach, a peninsula on the west coast of Ireland, to test its suitability as tool for ICZM. In addition, the paper uses the BPA methodology to explore the contrast between scientific/strategic and local attitudes towards the management of a coastal area of environmental importance. Pronounced differences between the two are found and the implications for both BPA and ICZM are discussed. The spatial and participatory nature of the BPA process and the explicit treatment of risk the framework exhibits suggest there is scope for it to become a useful tool for ICZM. It also has the potential to act as a routine way of quantifying the “attitude gap” between the scientific community and the local community when managing a unique coastal area.     

New and regenerated production in the Almeria-Oran front area,eastern Alboran Sea

Uptake and regeneration of nitrogen in the Almeria-Oran frontal zone (SW Mediterranean) and adjacent (Atlantic and Mediterranean) systems were studied during the Almofront I cruise (JGOFS-France). The frontal zone was characterized by an upsloping of nitracline from about 50 m in the adjacent systems to 25–30 m within. Along with nitrate, ammonium, chlorophyll a and particulate organic nitrogen also were at higher concentrations in the frontal zone than in the adjacent waters.The nitrate uptake rates were significantly higher in the frontal zone (up to 6.4 nmol l⁻¹ h⁻¹) than in the Atlantic and Mediterranean waters (generally <1 nmol l⁻¹ h⁻¹) indicating a significant increase of new production at the front. This increase was related to the upsloping of the nitracline as shown by the significant correlation (p<0.05) between new production and depth of the nitracline. The new production in the Almeria-Oran was much lower than those recorded in other oceanic and coastal fronts. This could be related to the fact that the nitracline did not rise up to the surface and the high concentrations of nitrate were confined to deeper layers where the ambient light intensity was less. Nitrate uptake in the frontal zone was significantly higher, by 1.7–5.8 times (average 4.2), than the calculated diffusive flux of nitrate, suggesting that vertical advection may be an important source of nitrate. New production rates at the front were also significantly higher (3–9 times, average 5.8) than the PON flux to 100 m depth estimated by sediments traps (Journal of Marine Systems 5, 377–389), suggesting a strong decoupling between surface production and downward flux of POM in the frontal zone.The north–south gradient observed with different parameters indicates the presence of a transfrontal secondary circulation. This distribution also suggests that the primary production in the front is initially nitrate-based, with a diatom-herbivore food chain, whereas regenerated production, associated with an intense recycling of organic matter, later becomes progressively important in time and space.     

Remote sensing and GIS-based integrated analysis of coastal changes and their environmental impacts in Lingding Bay,Pearl River Estuary,South China

Substantial changes are taking place in the coastal landscape as a result of rapid urbanization. A series of environmental and resource problems have emerged owing to rapid urban development, including encroachment of agricultural land, land reclamation, silt deposition in rivers, and severe flooding. These problems have had a significant impact on sustainable development in Lingding Bay, the largest estuary of the Pearl River. This paper demonstrates that remote sensing can be effective in monitoring the dynamics of coastal zones, such as coastline movement, urban expansion, land-use changes, and migration of shoals and deep-water channels. Remote sensing data from 1978 to 1998 were used to detect the accelerating changes that have taken place in the study area. A hybrid approach has proved to be an effective way of improving remote sensing image classification, with multi-temporal compound imaging, for coastal change analysis. Geographic information system (Intergraph's modular GIS environment, MGE) software was used to assist planners in the analysis of such changes, by combining the maps from 1974, 1989 to 1997 and integrating the multiple (spatial and attribute) databases. The result demonstrates that: (1) the Pearl River estuary is being reclaimed, estuarine waterways are getting narrower; the area of water near Humen town has narrowed by 4–6 km; (2) shoals in Lingding Bay have reduced the area of water by 114 km² over the past 23 years; the area of deep-water channels has declined by ∼24 km², even with dredging; on average, the area of water has decreased by 5.9 km² annually; western channels migrated eastwards 0.8 and 1.1 km during the first and second 10-year period, respectively; according to this scenario, the western channel will disappear from Lingding Bay in approximately 183 years; (3) land-use changes: 92% of shoal reclamation occurred in the 1980s and 80% of waterway reclamation happened during the 1990s; Panyu District of Guangzhou city leads the table in land reclamation, Zhongshan city is second, and Zhuhai city third; the area of reclamation in the last 10 years is slightly more (1.18 times) than in the previous 10 years, in particular, there was a 1.6- and 1.8-fold increase, respectively, for the Zhongshan and Zhuhai coastal regions; at the current rate of reclamation, Tangjia Bay in Zhuhai and Jiaoyi Bay in Dongwan will vanish in approximately 25 and 70 years, respectively; the decline of the bays will cause large-scale destruction of the aquatic environment—the consequences should not be ignored. The impact of such changes on flood control and prevention, and coastal planning, are also discussed. We stress the importance of regulating and controlling the long-term development of coastal areas in the Pearl River Delta.     

Egg production of turbot,Scophthalmus maximus,in the Baltic Sea

In the brackish water Baltic Sea turbot spawn at ~ 6–9 psu along the coast and on offshore banks in ICES SD 24–29, with salinity influencing the reproductive success. The potential fecundity (the stock of vitellogenic oocytes in the pre-spawning ovary), egg size (diameter and dry weight of artificially fertilized 1-day-old eggs) and gonad dry weight were assessed for fish sampled in SD 25 and SD 28. Multiple regression analysis identified somatic weight, or total length in combination with Fulton's condition factor, as main predictors of fecundity and gonad dry weight with stage of maturity (oocyte packing density or leading cohort) as an additional predictor. For egg size, somatic weight was identified as main predictor while otolith weight (proxy for age) was an additional predictor. Univariate analysis using GLM revealed significantly higher fecundity and gonad dry weight for turbot from SD 28 (3378–3474 oocytes/g somatic weight) compared to those from SD 25 (2343 oocytes/g somatic weight), with no difference in egg size (1.05 ± 0.03 mm diameter and 46.8 ± 6.5 μg dry weight; mean ± sd). The difference in egg production matched egg survival probabilities in relation to salinity conditions suggesting selection for higher fecundity as a consequence of poorer reproductive success at lower salinities. This supports the hypothesis of higher size-specific fecundity towards the limit of the distribution of a species as an adaptation to harsher environmental conditions and lower offspring survival probabilities. Within SD 28 comparisons were made between two major fishing areas targeting spawning aggregations and a marine protected area without fishing. The outcome was inconclusive and is discussed with respect to potential fishery induced effects, effects of the salinity gradient, effects of specific year-classes, and effects of maturation status of sampled fish.     

Assessment of tsunami hazard for coastal areas of Shandong Province,China

Shandong province is located on the east coast of China and has a coastline of about 3100 km. There are only a few tsunami events recorded in the history of Shandong Province, but the tsunami hazard assessment is still necessary as the rapid economic development and increasing population of this area. The objective of this study was to evaluate the potential danger posed by tsunamis for Shandong Province. The numerical simulation method was adopted to assess the tsunami hazard for coastal areas of Shandong Province. The Cornell multi-grid coupled tsunami numerical model (COMCOT) was used and its efficacy was verified by comparison with three historical tsunami events. The simulated maximum tsunami wave height agreed well with the observational data. Based on previous studies and statistical analyses, multiple earthquake scenarios in eight seismic zones were designed, the magnitudes of which were set as the potential maximum values. Then, the tsunamis they induced were simulated using the COMCOT model to investigate their impact on the coastal areas of Shandong Province. The numerical results showed that the maximum tsunami wave height, which was caused by the earthquake scenario located in the sea area of the Mariana Islands, could reach up to 1.39 m off the eastern coast of Weihai city. The tsunamis from the seismic zones of the Bohai Sea, Okinawa Trough, and Manila Trench could also reach heights of >1 m in some areas, meaning that earthquakes in these zones should not be ignored. The inundation hazard was distributed primarily in some northern coastal areas near Yantai and southeastern coastal areas of Shandong Peninsula. When considering both the magnitude and arrival time of tsunamis, it is suggested that greater attention be paid to earthquakes that occur in the Bohai Sea. In conclusion, the tsunami hazard facing the coastal area of Shandong Province is not very serious; however, disasters could occur if such events coincided with spring tides or other extreme oceanic conditions. The results of this study will be useful for the design of coastal engineering projects and the establishment of a tsunami warning system for Shandong Province.     

The influence of the south-west monsoon upon the nutrient biogeochemistry of the Arabian Sea

Variations in the nutrient concentrations were studied during two cruises to the Arabian Sea. The situation towards the end of the southwest monsoon season (September/October 1994) was compared with the inter-monsoonal season during November and December 1994. Underway surface transects showed the influence of an upwelling system during the first cruise with deep, colder, nutrient-rich water being advected into the surface mixed layer. During the southwesterly monsoon there was an area of coastal Ekman upwelling, bringing colder water (24.2°C) into the surface waters of the coastal margin. Further offshore at about 350 km there was an area of Ekman upwelling, as a result of wind-stress curl, north of the Findlater Jet axis; this area also had cooler surface water (24.6°C). Further offshore (>1000 km) the average surface temperatures increased to >27°C. These waters were oligotrophic with no evidence of the upwelling effects observed further inshore. In the upwelling regions nutrient concentrations in the close inshore coastal zone were elevated (NO₃=18 μmol l^-1, PO₄=1.48 μmol l^-1); higher concentrations also were measured at the region of offshore upwelling off the shelf, with a maximum nitrate concentration of 12.5 μmol l^-1 and a maximum phosphate concentration of 1.2 μmol l^-1. Nitrate and phosphate concentrations decreased with increasing distance offshore to the oligotrophic waters beyond 1400 km, where typical nitrate concentrations were 35.0 nmol l^-1 (0.035 μmol l^-1) in the surface mixed layer. A CTD section from the coastal shelf, to 1650 km offshore to the oligotrophic waters, clearly showed that during the monsoon season, upwelling is one of the major influences upon the nutrient concentrations in the surface waters of the Arabian Sea off the coast of Oman. Productivity of the water column was enhanced to a distance of over 800 km offshore. During the intermonsoon period a stable surface mixed layer was established, with a well-defined thermocline and nitracline. Surface temperature was between 26.8 and 27.4°C for the entire transect from the coast to 1650 km offshore. Nitrate concentrations were typically between 2.0 and 0.4 μmol l^-1 for the transect, to about 1200 km where the waters became oligotrophic, and nitrate concentrations were then typically 8–12 nmol l^-1. Ammonia concentrations for the oligotrophic waters were typically 130 nmol l^-1, and are reported for the first time in the Indian Ocean. The nitrogen/phosphorus (N/P) ratios suggest that phytoplankton production was potentially nitrogen-limited in all the surface waters of the Arabian Sea, with the greatest nitrogen limitation during the intermonsoon period.     

Anticyclonic eddies in the Norwegian Sea; their generation,evolution and impact on primary production

Altimetry and ocean color observations are used in combination with a coupled physical-primary production ocean model to investigate anticyclonic eddies at two locations in the Norwegian Sea. Of particular interest are the formation of the anticyclonic eddies, and their influence on primary production. The formation of these anticyclonic eddies are due to baroclinic instabilities set up by shifts in the wind in north/south direction, leading to simultaneously formation of eddies throughout the area. After a density stratification develops in the upper 100 m of the water column, the anticyclones become a subsurface lens of well mixed water with the characteristics of intra-thermocline eddies. The deep mixed layer inside anticyclonic eddies delay phytoplankton bloom by approximately two weeks compared to the surrounding areas. As the mixed layer within the anticyclones become smaller than the critical depth, the combination of this and sufficiently high nutrient levels support a phytoplankton bloom. From the satellite observations, there is an evidence of phytoplankton being advected toward the center of the eddies, but also of isolated phytoplankton blooms within the intra-thermocline eddies. The combined use of a numerical model and satellite observations provides three-dimensional information on the structure and properties of both eddies and primary production. The presented model is particularly useful in cloud-covered areas where ocean color images are frequently unavailable.     

Short-term statistics of waves measured off Ratnagiri,eastern Arabian Sea

The short-term wave characteristics are required for design and operation of industrial facilities within the coastal areas. Water surface displacement measured using waverider buoy moored at 13 m water depth in the eastern Arabian Sea off the west coast of India have been analyzed to study the short-term statistics of waves covering full one year period. The study indicates that the values of the observed maximum wave height as a function of duration are not consistent with the theoretical expected value. There is significant variation (1.29–2.19) in the ratio between highest 1% wave and significant wave height compared to the theoretical value of 1.67. The data recorded at 13 m water depth indicates that the significant wave height is ∼8% lower than that predicted by the conventional Rayleigh distribution. The theoretical bivariate log-normal distribution represents the joint distributions of wave heights and periods for the study area.     

ENSO and salinity changes in the Ciénaga Grande de Santa Marta coastal lagoon system,Colombian Caribbean

Salinity changes in the Ciénaga Grande de Santa Marta and Pajarales Complex coastal lagoon system in northern Colombia, and their relation with local rainfall, tributaries' streamflow and ENSO, are analyzed. Being markedly low (<1321 mm yr⁻¹), local rainfall is assumed to be insignificant for mean salinity changes. The non-linear model proposed explains the variations in salinity and tributaries' streamflow with ENSO intensity, measured as Southern Oscillation Index (SOI) anomaly. Streamflows are directly and salinity inversely correlated with SOI. Model analysis allowed to discriminate between natural and hydraulic management situations and also how the occurrence of different environmental scenarios reflected on salinity changes. The link between global climate variability and local conditions becomes clearer and worthy to be brought into account in management and decision making processes dealing with continental as well as other marine and coastal aquatic environments in the Caribbean region.     

Dianeutral mixing,transformation and transport of the deep water of the Indian Ocean

The realization of North Atlantic Deep Water (NADW) replacement in the deep northern Indian Ocean is crucial to the “conveyor belt” scheme. This was investigated with the updated 1994 Levitus climatological atlas. The study was performed on four selected neutral surfaces, encompassing the Indian deep water from 2000 to 3500 m. The Indian deep water comprises three major water masses: NADW, Circumpolar Deep Water (CDW) and North Indian Deep Water (NIDW). Since NADW flowing into the southwest Indian Ocean is largely blocked by the ridges (the Madagascar Ridge in the east and Davie Ridge in the north in the Mozambique Channel) and NIDW is the only source in the northern Indian Ocean that cannot provide a large amount of volume transport, CDW has to be a major source for the Indian deep circulation and ventilation in the north. Thus the question of NADW replacement becomes that of how the advective flows of CDW from the south are changed to be upwelled flows in the north—a water-mass transformation scenario. This study considered various processes causing motion across neutral surfaces. It is found that dianeutral mixing is vital to achieve CDW transformation. Basin-wide uniform dianeutral upwelling is detected in the entire Indian deep water north of 32°S, somewhat concentrated in the eastern Indian Ocean on the lowest surface. However, the integrated dianeutral transport is quite low, about a net of 0.2 Sv (1 Sv=10⁶ m³ s^-1) across the lowermost neutral surface upward and 0.4 Sv across the uppermost surface upward north of 32°S with an error band of about 10–20% when an uncertainty of half-order change in diffusivities is assumed. Given about 10–15% of rough ridge area where dianeutral diffusivity could be about one order of magnitude higher (10^-4 m² s^-1) due to internal-wave breaking, the additional amount of increased net dianeutral transport across the lowest neutral surface is still within that error band. The averaged net upward transport in the north is matched with a net downward transport of 0.3 Sv integrated in the Southern Ocean south of 45°S across the lowermost surface. With the previous works of You (1996. Deep Sea Research 43, 291–320) in the thermocline and You (Journal of Geophysical Research) in the intermediate water combined, a schematic dianeutral circulation of the Indian Ocean emerges. The integrated net dianeutral upwelling transport shows a steady increase from the deep water to the upper thermocline (from 0.2 to 4.6) north of 32°S. The dianeutral upwelling transport is accumulated upward as the northward advective transport provided from the Southern Ocean increases. As a result, the dianeutral upwelling transport north of 32°S can provide at least 4.6 Sv to south of 32°S from the upper main thermocline, most likely to the Agulhas Current system. This amount of dianeutral upwelling transport does not include the top 150–200 m, which may contribute much more volume transport to the south.     

Deep-sea suprabenthos assemblages (Crustacea) off the Balearic Islands (western Mediterranean): Mesoscale variability in diversity and production

The composition of suprabenthic crustacean assemblages, their diversity, production (P) and production/biomass (P/B) ratios, were analyzed at species level along two transects situated to the north (N) and south (S) of Mallorca (Balearic Islands, western Mediterranean) at depths between 134 m and 760 m, based on a ca. bi-monthly sampling performed between August 2003 and June 2004. Differences with depth and season in assemblage composition and diversity were analyzed as a function of the contrasting environmental features (e.g. water mass dynamics) of the two areas. We identified 187 species (18 decapods, 5 euphausiids, 16 mysids, 76 gammaridean amphipods, 13 hyperiids, 1 caprellid, 21 isopods and 37 cumaceans). Substantial mesoscale variability in the deep-sea suprabenthic assemblages coupled with diversity trends between the N and S transects were found. Seasonality was the most important gradient influencing the dynamics of suprabenthos over the upper (350 m) and middle (650–750 m) slope in the N area. Conversely, the S area appeared to be more stable temporally with depth as the main gradient inducing assemblage differences. Different depth-related patterns were observed both for diversity and P/B. To the north diversity was very low at the shelf-break, increasing on the upper-slope (H′ > 3.00) and then decreasing again on the middle-slope. To the south diversity increased smoothly downward, reaching the highest values on the middle-slope. Regarding productivity, P/B was highest at intermediate depths to the north (over ca. 450–500 m), while to the south highest P/Bs were found deeper (over ca. 600–650 m). The higher P/B at intermediate depths found along N are likely due to higher % of organic matter (OM) in sediments, a product of oceanographic frontal systems. In particular, P/B was higher along N among omnivores and detritus feeders (e.g. Andaniexis mimonectes, Lepechinella manco and combined cumaceans), coupled to enriched OM in sediments, while along S mesoplanktonic carnivores (Rhachotropis spp.) had higher P/Bs. We conclude that on the north slope the influence of frontal systems and more active flow dynamics of different water masses (WIW and LIW) increases natural disturbance in the area, increasing productivity and diversity of suprabenthic peracarids in the Benthic Boundary Layer. Also, species showed a displacement of their average distributions (their Centres of Gravity, CoG) to shallower depths along N, which is another indicator of more favorable habitat conditions for suprabenthos in the 400–500 m range at N.