Is greenhouse gas forcing a plausible explanation for the observed warming in the Baltic Sea catchment area?

We investigated whether anthropogenic forcing is a plausible explanation for the observed warming in the Baltic Sea catchment area. Therefore, we compared the most recent trends in the surface temperature over land with anthropogenic climate change projections from regional climate model simulations. We analyzed patterns of change with different spatio-temporal resolutions. The observed annual area-mean change in the daily-mean temperature was consistent with the anthropogenic climate change signal. This finding was robust to the removal of the signal of the North Atlantic Oscillation. In contrast to the annual area-mean change, we found little consistency in both annual cycle and spatial variability of the observed and projected changes

The German Bight (North Sea) is a nursery area for both locally and externally produced sprat juveniles

To better understand the role of the German Bight (GB) as a nursery area for juvenile North Sea sprat Sprattus sprattus we sought to determine whether the area may receive only locally or also externally produced offspring. We sampled juveniles during 3 trawl surveys in the GB in August, September, and October 2004 and applied otolith microstructure analysis in order to reconstruct their distributions of the day-of-first-increment-formation (dif). These were contrasted with spatial and seasonal patterns of sprat egg abundance in the GB and its adjacent areas, observed during 6 monthly plankton surveys. It was found that the majority of juveniles originated mainly from April/May 2004, coinciding with high spawning activity west of the GB, whereas spawning and larval production inside the GB peaked notably later, in May/June. This indicated that a large proportion of juveniles was produced outside the GB and transported subsequently into it through passive and/or active migration. Shifts to later mean difs from one survey to the next and length distributions indicative of the simultaneous presence of multiple cohorts, supported the notion that the GB is a complex retention and nursery area for sprat offspring from different North Sea spawning grounds and times. Later born juveniles had significantly faster initial growth rates than earlier born conspecifics, which was likely temperature-mediated, given the strong correlation between back-calculated growth histories and sea surface temperature as a proxy for thermal histories of juveniles (r(2) = 0.52). (C) 2009 Elsevier B.V. All rights reserved

Spectral quantification of nonlinear behaviour of the nearshore seabed and correlations with potential forcings at Duck, N.C., U.S.A

Local bathymetric quasi-periodic patterns of oscillation are identified from monthly profile surveys taken at two shore-perpendicular transects at the USACE field research facility in Duck, North Carolina, USA, spanning 24.5 years and covering the swash and surf zones. The chosen transects are the two furthest (north and south) from the pier located at the study site. Research at Duck has traditionally focused on one or more of these transects as the effects of the pier are least at these locations. The patterns are identified using singular spectrum analysis (SSA). Possible correlations with potential forcing mechanisms are discussed by 1) doing an SSA with same parameter settings to independently identify the quasi-periodic cycles embedded within three potentially linked sequences: monthly wave heights (MWH), monthly mean water levels (MWL) and the large scale atmospheric index known as the North Atlantic Oscillation (NAO) and 2) comparing the patterns within MWH, MWL and NAO to the local bathymetric patterns. The results agree well with previous patterns identified using wavelets and confirm the highly nonstationary behaviour of beach levels at Duck; the discussion of potential correlations with hydrodynamic and atmospheric phenomena is a new contribution. The study is then extended to all measured bathymetric profiles, covering an area of 1100m (alongshore) by 440m (cross-shore), to 1) analyse linear correlations between the bathymetry and the potential forcings using multivariate empirical orthogonal functions (MEOF) and linear correlation analysis and 2) identify which collective quasi-periodic bathymetric patterns are correlated with those within MWH, MWL or NAO, based on a (nonlinear) multichannel singular spectrum analysis (MSSA). (...continued in submitted paper)Comment: 50 pages, 3 tables, 8 figure

Räime Clupea harengus membras varajaste elustaadiumide ökoloogia Läänemere kirdeosas

Väitekirja elektrooniline versioon ei sisalda publikatsioone.Läänemeres elav räim (Clupea harengus membras) on Atlandi heeringa (Clupea harengus L.) kääbustunud vorm, kes on kohastunud elama riimveelise Läänemere väga varieeruvates keskkonnatingimustes. Morfoloogiliste tunnuste alusel eristatakse Läänemere räimel kahte erinevat sesoonset kudemistüüpi – kevad ja sügiskudu räim. Käesolevas töös on analüüsitud räimevastsete toitumisaktiivsuse ja nende sooltorust leitud saakloomade dünaamikat ning leitut on seostatud valitud eluta- ja eluskeskkonna teguritega. Räimevastsete toidus oli valdavaks liigiks aerjalgne Eurytemora affinis, kusjuures kõikide teiste liikide isendeid leiti vaid juhuslikult. Räimevastete toitumisaktiivsus seostus erinevate keskkonnateguritega, ning seosed varieerusid sõltuvalt räimevastse arengust. Kalade varajaste elustaadiumite arvukuse dünaamika uuringute üks praktilisi väljundeid on juba möödunud sajandist alates seostunud kalavaru täiendi suuruse hindamisega. Vaatamata järjepidevatele pingutustele ei ole selles valdkonnas väga suuri edusamme saavutatud. Me leidsime, et suurte räimevastete arvukus seostus usaldusväärselt räimevaru täiendi arvukusega, ja on seega oluline kalandusandmetest mitte-sõltuv lisategur hindamaks kujuneva räimevaru suurust lähitulevikus. Käesolevas töös käsitletud üheksateistkümne Liivi lahe kevadräime varajaste elustaadiumidega seonduva teguri pika-ajalisel analüüsil (perioodil 1957-2010) selgitasime a) kas ja millal on toimunud radikaalsed pöördumatud muutused (ehk nn. režiiminihked), b) millised tegurid või nende kombinatsioon mõjutavad nimetatud muutusi ning c) kas režiiminihked süsteemis toimusid sünkroonselt räime varajaste elustaadiumidega. Leitu põhjal võib järeldada, et ökosüsteemis saab eristada kahte erinevat seisundit. Esimene neist kestis perioodil 1957–1985, millele järgnes sujuv, pikka aega kestnud üleminek (1986–1991) uude seisundisse, alates 1992 kuni tänapäevani. Sealjuures, tugevaim signaal keskkonnaseisundi muutustele pärines eluta keskkonnast ning seostus mere termilise režiimi muutusega. Analüüsi kaasatud fenoloogiliste ning eluskeskkonna komponente koondavate aegridade olulisus režiiminihkele oli seega vähemtähtis.Baltic herring (Clupea harengus membras) is Atlantic herring (Clupea harengus L. 1758) sub-species that is adapted to the prevailing spatio-temporally varying heterogeneous environmental conditions of the Baltic Sea. On the basis of morphometric and meristic characters, two groups – spring and autumn spawners – were distinguished in the Baltic Sea. In the present thesis, feeding ecology of the larval spring-spawning herring was studied in relation to selected abiotic and biotic parameters. The copepod Eurytemora affinis was the strongly dominating dietary item during all years while other prey was ingested only sporadically. Feeding activity of herring larvae was affected by different environmental variables and the relationships varied among the size classes of herring larvae. We have found that the abundance of large larvae correlated well with the year class strength of the Gulf of Riga (GoR) spring spawning herring population. This should be considered as an important fisheries independent finding in practical terms as it allows preliminary estimations to be made much earlier than the availability of the stock assessment results. The multivariate shiftogram approach by pooling nineteen different herring early life-history stages relevant variables was applied to identify a) whether and when the abrupt changes (also called as regime shifts) take place in the herring-relevant data series in the GoR ecosystem, b) which factors or their combination are responsible for the observed ecosystem-level changes and c) whether changes at the ecosystem level appeared synchronously with those observed in phenology and abundance-related single time series of larval herring. It appeared that two distinct ecosystem states of the GoR could be identified. The first state occurred between 1957–1985, followed by a smooth transition period, lasting from 1986–1991 and has resulted in a new ecosystem phase since 1992 onwards. The GoR ecosystem seem to be mainly regulated by abiotic conditions, especially those related to the thermal regime (sea surface temperature in spring and summer, winter air temperature and timing of ice retreat) while phenological and biotic time-series (timing of maximum abundance of herring larvae, onset of herring larvae and mean abundance of Eurytemora affinis adults) had a substantially minor role

Spatio-temporal dynamics of a fish predator: Density-dependent and hydrographic effects on Baltic Sea cod population

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Geographical Studies of Underwater Light Dynamics in the Coastal Archipelago of SW Finland, Baltic Sea

The underwater light field is an important environmental variable as it, among other things, enables aquatic primary production. Although the portion of solar radiation that is referred to as visible light penetrates water, it is restricted to a limited surface water layer because of efficient absorption and scattering processes. Based on the varying content of optical constituents in the water, the efficiency of light attenuation changes in many dimensions and over various spatial and temporal scales. This thesis discusses the underwater light dynamics of a transitional coastal archipelago in south-western Finland, in the Baltic Sea. While the area has long been known to have a highly variable underwater light field, quantified knowledge on the phenomenon has been scarce, patchy, or non-existent. This thesis focuses on the variability in the underwater light field through euphotic depths (1% irradiance remaining), which were derived from in situ measurements of vertical profiles of photosynthetically active radiation (PAR). Spot samples were conducted in the archipelago of south-western Finland, mainly during the ice-free growing seasons of 2010 and 2011. In addition to quantifying both the seasonal and geographical patterns of euphotic depth development, the need and usability of underwater light information are also discussed. Light availability was found to fluctuate in multiple dimensions and scales. The euphotic depth was shown to have combined spatio-temporal dynamics rather than separate changes in spatial and temporal dimensions. Such complexity in the underwater light field creates challenges in data collection, as well as in its utilisation. Although local information is needed, in highly variable conditions spot sampled information may only poorly represent its surroundings. Moreover, either temporally or spatially limited sampling may cause biases in understanding underwater light dynamics. Consequently, the application of light availability data, for example in ecological modelling, should be made with great caution.Vesien kirkkaus tai vaihtoehtoisesti sameus vaikuttaa vedenalaisluonnon toimintaan monin tavoin. Valaistusolosuhteiden merkitys ympäristömuuttujana korostuu erityisesti elämää ylläpitävän perustuotannon kautta, sillä näkyväksi valoksi kutsumamme auringonsäteilyn osuus mahdollistaa yhteyttämisen niin vedessä kuin kuivalla maallakin. Vedessä valo ei kuitenkaan tunkeudu pintakerrosta syvemmälle, sillä erilaiset absorptio- ja sirontaprosessit vaimentavat sen etenemistä tehokkaasti. Valosäteilyn vaimenemistehokkuus taas vaihtelee moniulotteisesti vedessä olevien vaimentavien ainesten pitoisuuksien mukaisesti. Tässä väitöskirjassa käsitellään vedenalaisen valon vaihteludynamiikkaa Itämeren rannikolla. Tutkimus keskittyy Lounais-Suomen saaristoon, joka laajana saaristovaihettumavyöhykkeenä tarjoaa monipuolisen ja vaihtelevan tutkimusalueen. Tämän saaristoalueen on jo pitkään tiedetty olevan valaistusolosuhteiltaan hyvin vaihteleva, mutta tarkkaa tutkimustietoa näistä vaihteluista oli saatavilla hyvin vähän, jos lainkaan. Väitöskirja perehtyy vedenalaisten valaistusolosuhteiden vaihteluun käsittelemällä erityisesti veden valaistun pintakerroksen, eli eufoottisen kerroksen, paksuutta ja sen muutoksia. Eufoottiset syvyydet, joissa 1 % pintakerroksen läpäisevästä auringonsäteilystä on jäljellä, määriteltiin jäättömänä aikana kasvukausina 2010 ja 2011 mitatuista valomäärän syvyysprofiileista. Sen lisäksi, että tutkimuksessa tuotettiin mitattua tietoa valaistun kerroksen alueellisista vaihettumista ja kasvukauden aikaisista muutoksista, työssä pohditaan myös valomäärätiedon tarvetta ja sen soveltamiseen liittyviä haasteita. Koska valon saatavuuden muutokset ovat alueellis-ajallisesti moniulotteisia ja -tasoisia, ei edustavan aineiston kerääminen ja edes kattavan tiedon tehokas hyödyntäminen ole yksiselitteistä tai ongelmatonta. Alueella, jossa olosuhteiden vaihtelut ovat suuria, paikallisen tason tiedonkeruun merkitys korostuu, mutta samalla yksittäisten mittauspisteiden edustavuus voi olla hyvinkin heikkoa. Joko alueellisesti tai ajallisesti rajalliset kenttämittaukset taas saattavat aiheuttaa vääristyneen yleiskuvan veden valaistusolosuhteista. Näin ollen valoaineistojen soveltaminen, esimerkiksi ekologiseen mallinnukseen, on syytä tehdä harkiten ja huolella.Siirretty Doriast

High-resolution GPS tracking reveals sex differences in migratory behaviour and stopover habitat use in the lesser black-backed gull Larus fuscus

Sex-, size-or age-dependent variation in migration strategies in birds is generally expected to reflect differences in competitive abilities. Theoretical and empirical studies thereby focus on differences in wintering areas, by which individuals may benefit from avoiding food competition during winter or ensuring an early return and access to prime nesting sites in spring. Here, we use GPS tracking to assess sex-and size-related variation in the spatial behaviour of adult Lesser Black-backed Gulls (Larus fuscus) throughout their annual cycle. We did not find sex-or size-dependent differences in wintering area or the timing of spring migration. Instead, sexual differences occurred prior to, and during, autumn migration, when females strongly focussed on agricultural areas. Females exhibited a more protracted autumn migration strategy, hence spent more time on stopover sites and arrived 15 days later at their wintering areas, than males. This shift in habitat use and protracted autumn migration coincided with the timing of moult, which overlaps with chick rearing and migration. Our results suggest that this overlap between energy-demanding activities may lead females to perform a more prolonged autumn migration, which results in spatiotemporal differences in foraging habitat use between the sexes