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    ABSTRACT: Sperm whale (Physeter macrocephalus) populations were severely depleted by commercial whaling worldwide in the 18th through the 20th century. Consequently, in 1970, this species was listed in the United States as an endangered species. To date, accurate information on the abundance and distribution of sperm whales in offshore areas of the North Pacific are scant. Sperm whales regularly produce high intensity sounds for navigation, prey detection, and communication. Thus, this species can be very effectively monitored using passive acoustic techniques especially in remote and inaccessible locations such as the Gulf of Alaska (GOA). In this study, a Passive Aquatic Listener (PAL) was deployed at Ocean Station PAPA (50°N, 145°W) in the GOA between 2007 and 2012 to monitor the seasonal occurrence of sperm whales in the area. Preliminary results indicate that within the 5-year deployment period sperm whales were acoustically present year round and that the number of acoustic sperm whale detections showed a seasonal trend with slightly higher numbers during the summer months. We are currently investigating the linkage between the occurrence of sperm whales and environmental conditions (e.g., Pacific Decadal Oscillation index) in the study area. [Funding from the Office of Naval Research.].
    The Journal of the Acoustical Society of America 11/2013; 134(5):3971.
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    ABSTRACT: The present study deals with the development, application and evaluation of a modelling tool, implemented along with a field sampling program, in a limited coastal area in the Northeast Aegean. The aim was to study, understand and quantify physical circulation and water column ecological processes in a high resolution simulation of a past annual cycle. The marine ecosystem model consists of a three dimensional hydrodynamic component suitable for coastal areas (Princeton Ocean Model) coupled to a simple ecological model of five variables, namely, phytoplankton, nitrate, ammonia, phosphate and dissolved organic carbon concentrations. The ecological parameters (e.g. half saturation constants and maximum uptake rates for nutrients) were calibrated using a specially developed automated procedure. Model errors were evaluated using qualitative, graphic techniques and were quantified with a number of goodness-of-fit measures. Regarding physical variables, the goodness-of-fit of model to field data varied from fairly to quite good. Indicatively, the cost function, expressed as mean value per sampling station, ranged from 0.15 to 0.23 for temperature and 0.81 to 3.70 for current speed. The annual cycle of phytoplankton biomass was simulated with sufficient accuracy (e.g. mean cost function ranging from 0.49 to 2.67), partly attributed to the adequate reproduction of the dynamics of growth limiting nutrients, nitrate, ammonia and the main limiting nutrient, phosphate, whose mean cost function ranged from 0.97 to 1.88. Model results and field data provided insight to physical processes such as the development of a wind-driven, coastal jet type of surface alongshore flow with a subsurface countercurrent flowing towards opposite direction and the formation of rotational flows in the embayments of the coastline when the offshore coastal current speed approaches values of about 0.1 m/s. The percentage of field measurements where the N:P ratio was found over 16:1 varied between stations from 57 to 65%, demonstrating the importance of phosphate as a limiting nutrient for phytoplankton growth. The model also successfully reproduced phytoplankton gradients, e.g. those developed almost all year round between the most eutrophic areas (city harbour with mean chlorophyll-a concentration of 1.08 μg/L and decreasing biomass by over 40 mg C/m3 from surface to the bottom layer) and the oligotrophic open waters (mean chlorophyll-a concentration of 0.14 μg/L).
    Estuarine Coastal and Shelf Science 07/2013; 126:44–60.
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    ABSTRACT: The exploration of processes leading to coastal eutrophication is a major challenge in ecological research, particularly in light of important new policies such as the European Water Framework Directive. In the present study primary production (in terms of chlorophyll α – chl α) is modeled based on a number of abiotic parameters using model trees (MTs), a machine learning (ML) approach whereby linear regressions are induced within homogeneous subsets of samples (tree leaves). Standardized regression was applied to determine the relative weight of abiotic parameters in the MT tree leaves whereas the efficiency of the MT method in chl α prediction was tested against neural networks (NNs) which is the most frequently used ML approach, and the classical multiple linear regression (MLR). To assess the efficiency of models to describe eutrophication-related responses under different environmental conditions, the methods were applied on a coastal ecosystem affected by terrestrial runoff for two meteorologically contrasting annual cycles: a typical dry ('04–'05) and a typical wet ('09–'10). MTs showed increased predictive power in chl α prediction attributed to the discrimination of input data space into tree leaves, instead of using a uniform space as in NNs and MLR. By grouping samples of each tested annual cycle (wet and dry) on a seasonal basis into discrete groups/leaves, MTs offer a much more explanatory description of ecosystem status than NNs and MLR. The discriminating variables forming tree leaves and the weighing coefficients of Linear Models (LMs) in each leaf provided a useful scaling of abiotic parameters driving chl α dynamics. The MT method is thus proposed as an efficient tool for obtaining insights into ecosystem processes leading to eutrophication events in coastal ecosystems and a useful component in integrated coastal zone management.
    Estuarine Coastal and Shelf Science 12/2012; 115:210-217.
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    ABSTRACT: Cited By (since 1996): 4, Export Date: 15 January 2013, Source: Scopus, CODEN: JMASE, doi: 10.1016/j.jmarsys.2011.07.009, Language of Original Document: English, Correspondence Address: Gregg, M.C.; Applied Physics Laboratory, School of Oceanography, Univ. of Washington, Seattle, WA 98105, United States; email: gregg@apl.washington.edu, References: Alexandri, M., Papanikolaou, D., Nomikou, P., Santorini volcanic field - new insights based on swath bathymetry (2003) Proceedings of the 2003 IUGG, Sapporo, Japan, , July;
    Journal of Marine Systems 01/2012; 89(1):30-47.
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    ABSTRACT: Export Date: 15 January 2013, Source: Scopus, Art. No.: C01015, doi: 10.1029/2011JC007488, Language of Original Document: English, Correspondence Address: Alford, M.H.; Applied Physics Laboratory, School of Oceanography, University of Washington, 1013 NE 40th St., Seattle, WA 98105, United States; email: malford@apl.washington.edu, References: Alford, M.H., Internal swell generation: The spatial distribution of energy flux from the wind to mixed layer near-inrtial motions (2001) Journal of Physical Oceanography, 31 (8 PART 2), pp. 2359-2368;
    Journal of Geophysical Research C: Oceans. 01/2012; 117(1).
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    ABSTRACT: Cited By (since 1996): 1, Export Date: 16 January 2013, Source: Scopus, CODEN: JEMBA, doi: 10.1016/j.jembe.2012.05.016, Language of Original Document: English, Correspondence Address: Dimitriadis, C.; Dept. of Marine Sciences, Faculty of Environment, University of the Aegean, Lesvos Island 81100, Greece; email: xdimitriadis@marine.aegean.gr, References: Basset, A., Sabetta, L., Sangiorgio, F., Pinna, M., Migoni, D., Fanizzi, F., Barbone, E., Beqiraj, S., Biodiversity conservation in Mediterranean and Black Sea lagoons: a trait-oriented approach to benthic invertebrate guilds (2008) Aquat. Conserv. Mar. Freshwat. Ecosyst., 18, pp. 4-15;
    Journal of Experimental Marine Biology and Ecology 01/2012; 426-427:53-59.
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    ABSTRACT: The Mediterranean Sea is a semienclosed basin connected with the open sea mainly through the Strait of Gibraltar. Due to the circulation pattern and the long residence time ranging between 80 and 100 years, the Mediterranean Sea is a sensitive environment to eutrophication pressures. The main body of water of the Mediterranean is characterized by very low nutrient concentrations, and therefore, the Mediterranean is classified among the most oligotrophic (very poor waters in nutrients) seas of the world's oceans. However, some coastal areas, mainly in the northern part of the basin, receive excessive loads of nutrients from sewage effluents, river fluxes, aquaculture farms, fertilizers, and industrial facilities, showing intense eutrophic phenomena with many adverse effects for the marine ecosystem and humans. Various national and international authorities, in addition to monitoring, have taken legal and administrative measures to mitigate eutrophication trends in the area. The Mediterranean environment is a good paradigm of integration of extensive legal framework, scientific knowledge, and administrative practices. The Barcelona Convention, the Mediterranean Action Plan, and European Union Directives on water quality and coastal management, together with scientific information derived from international research programs in the Mediterranean, provide a sound background for practical actions in eutrophication problems. In the present work, the problem of coastal eutrophication in the Mediterranean is reviewed in connection with public policies of the Mediterranean States based on national and international legislation and scientific knowledge on Mediterranean oceanography-ecology and actions coordinated by international bodies. These common actions and practices on coastal management are also discussed in relation to the need for sustainable development and protection of the coastal zone in the Mediterranean Sea.
    Environmental Monitoring and Assessment 09/2011; 184(8):4931-84.
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    ABSTRACT: The TRIX index used for the assessment of trophic status of coastal waters has been applied in many European seas (Adriatic, Tyrrhenian, Baltic, Black Sea, and North Sea). However, all these waters are characterized by high nutrient levels and phytoplankton biomass; index calibration based on systems that are principally eutrophic may introduce bias to the index scaling. In the present work the TRIX trophic index is evaluated using three standard sets of data characterizing oligotrophy, mesotrophy, and eutrophication in the Aegean (Eastern Mediterranean) marine environment. A natural eutrophication scale based on the TRIX index that is suitable to characterize trophic conditions in oligotrophic Mediterranean water bodies is proposed. This scale was developed into a five-grade water quality classification scheme describing different levels of eutrophication. It is questionable whether this index can form a universal index of eutrophication or the scaling of TRIX should be region specific.
    Environmental Monitoring and Assessment 07/2011; 178(1-4):257-69.
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    ABSTRACT: Simulated phytoplankton assemblages (species richness and allocation of cells to species) retaining the diversity, evenness, and redundancy of natural assemblages were generated in the present paper. The methodology was validated against phytoplankton data from coastal Mediterranean waters, characteristic of oligotrophy to eutrophication. Two modelling approaches were used: a descriptive based on the log series statistical distribution, and a mechanistic based on the random fraction niche-apportionment model. Two characteristic relationships extracted from field data (888 samples), relating species richness and the abundance of the most dominant species with cell density, formed the basis of the modelling procedure. Simulated assemblages generated by both log series and random fraction models closely matched the structure of natural phytoplankton assemblages, showing however differences in their behaviour and easiness of application. Simulation by the log series model resulted in a wider range of assemblage diversity, closer to reality compared to random fraction model. Nevertheless, the latter includes a stochastic element always present in field assemblages, it is mathematically simpler to be applied, and it is based on a sound theoretical basis linking assemblage structure and resource availability. The proposed simulated assemblages can be used in a variety of applications ranging from the development of systematic methodologies for water quality assessment to the incorporation of a multispecies phytoplankton component in biogeochemical dynamic models. (C) 2011 Elsevier B.V. All rights reserved
    Ecological Modelling 01/2011; 222(12):1922-1928.
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    ABSTRACT: The discriminating power of eutrophication assessment schemes is often affected by the intercorrelation between cause (nutrient concentrations) and response (phytoplankton biomass and diversity) variables. Principal component analysis, a multivariate data reduction technique producing new sets of uncorrelated variables, was applied on nitrate, nitrite, ammonia, phosphate and chlorophyll α concentrations from coastal waters in the Aegean Sea, Eastern Mediterranean, and the first principal component was derived and evaluated as a eutrophication index on an independent dataset. The index, a linear combination of the five variables with almost equal weights, was found efficient in discriminating levels of eutrophication and critical thresholds characterizing oligotrophy, mesotrophy and eutrophication were set. The applicability of these thresholds for the implementation of the European Water Framework Directive was also examined thereof a five-level water quality classification scheme was developed.
    Ecological Indicators. 03/2010; 10:178-183.
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