Taxon-specific prey response to the invasion of a pelagic invertebrate predator, revealed by comparison of pre- and post-invasion time series

2020 ◽  
Author(s):  
Heli Einberg ◽  
Riina Klais-Peets ◽  
Arno Põllumäe ◽  
Henn Ojaveer
Keyword(s):  
Time Series ◽  
Baltic Sea ◽  
Seasonal Abundance ◽  
Indigenous Species ◽  
Long Term Effects ◽  
Gulf Of Riga ◽  
Marine Realm ◽  
The Baltic ◽  
Non Indigenous Species

Abstract Quantification and attribution of the food web changes associated with the invasion of non-indigenous species in the marine realm often remain a challenge. One of the pelagic non-indigenous species of concern in the recent history of aquatic bioinvasions is the predatory cladoceran Cercopagis pengoi, which invaded the Baltic Sea in the early 1990s. While several studies have reported immediate declines in abundances of its potential prey, the long-term effects of C. pengoi on the food webs remain to be examined. Based on the long-term time series (1968–2018) in the Gulf of Riga (Baltic Sea), we found significant declines in abundance of the cladoceran Pleopis spp. and copepod Eurytemora affinis by 90 and 80%, respectively, are associated with the invasion of C. pengoi as well as significant alterations in seasonal abundance patterns of Pleopis spp., E. affinis and cladoceran Bosmina spp. The invasion of the non-indigenous predator has led to the changed prey abundance–temperature relationships. Special caution was taken in data preprocessing, to minimize the likelihood that observed changes in the zooplankton prey could be associated with factors other than the invasion of C. pengoi, such as temperature and storminess.

Meta-analysis on the ecological impacts of widely spread non-indigenous species in the Baltic Sea

2021 ◽  
pp. 147375
Author(s):  
Henn Ojaveer ◽  
Jonne Kotta ◽  
Okko Outinen ◽  
Heli Einberg ◽  
Anastasija Zaiko ◽  
...  
Keyword(s):  
Baltic Sea ◽  
Meta Analysis ◽  
Ecological Impacts ◽  
Indigenous Species ◽  
The Baltic Sea ◽  
The Baltic ◽  
Non Indigenous Species

scholarly journals SEA LEVEL VARIATIONS AT THE LATVIAN COASTAL HYDROLOGIC STATIONS

2016 ◽  
Vol 42 (2) ◽  
pp. 31-38
Author(s):  
Diāna Haritonova
Keyword(s):  
Time Series ◽  
Baltic Sea ◽  
Sea Level ◽  
The Baltic Sea ◽  
Gulf Of Riga ◽  
Water Level Variations ◽  
Sea Level Variations ◽  
Tidal Constituents ◽  
The Baltic ◽  
Tidal Variations

The objective of this paper is to analyse water level variations of the Baltic Sea on the Latvian coast. This is important because the Baltic Sea exhibits a number of remarkable phenomena. One of them is the sea level variations due to winds, complicated by the shape of the gulfs and islands. Under this influence the range of the sea level variations can reach 3 m on the coasts of gulfs. However, the tidal variations of the Baltic Sea range in the order of centimetres only. In the frame of this study, using hourly time series of the sea level records from 7 Latvian coastal hydrologic stations and employing spectral analysis, it has become feasible to identify diurnal and semi-diurnal tide existence both in the Gulf of Riga and in the Baltic Sea at the Latvian coast. Totally 4 main tidal constituents (O1, K1, M2, S2) have been identified. Additionally, nontidal frequency of 5 cycles per day has been detected in the sea level time series of the stations located in the Gulf of Riga.

scholarly journals Non-stationary analysis of water level extremes in Latvian waters, Baltic Sea, during 1961–2018

2020 ◽  
Author(s):  
Nadezhda Kudryavtseva ◽  
Tarmo Soomere ◽  
Rain Männikus
Keyword(s):  
Time Series ◽  
Baltic Sea ◽  
Water Level ◽  
Shape Parameter ◽  
Extreme Value Distribution ◽  
Scale Parameters ◽  
Stationary Analysis ◽  
Gulf Of Riga ◽  
Baltic Proper ◽  
The Baltic

Abstract. Analysis and prediction of water level extremes in the eastern Baltic Sea is a difficult task because of the contribution of various drivers to the water level, the presence of outliers in time series and possibly non-stationarity of the extremes owing to the changes in the atmospheric forcing. Non-stationary modelling of extremes was performed to the block maxima of water level derived from the time series at six locations in the Gulf of Riga and one location in the Baltic proper, Baltic Sea, during 1961–2018. Several parameters of the Generalised Extreme Value distribution of the measured water maxima both in the Baltic proper and in the interior of the Gulf of Riga exhibit statistically significant changes over these years. The most considerable changes occur to the shape parameter ξ. All stations in the interior of the Gulf of Riga experienced a regime shift: a drastic abrupt drop of the shape parameter from ξ ≈ 0.03 ± 0.02 to ξ ≈ −0.36 ± 0.04 around 1986 followed by an increase of a similar magnitude around 1990. This means a sudden switch from a Fréchet distribution to a three-parameter Weibull distribution and back. The water level extremes at Liepaja in the Baltic proper and Kolka at the entrance to the Gulf of Riga reveal significant linear trends in the location and scale parameters. This pattern indicates a different course of the water level extremes in the Baltic proper and the interior of the Gulf of Riga. The described changes may lead to greatly different projections for long-term behaviour of water level extremes and their return periods based on data from different intervals.

scholarly journals Seasonal and Decadal Variations of the Variance of the Synoptic and Mesoscale Sea Level Variability in the Baltic Sea

Water ◽  
2021 ◽  
Vol 13 (13) ◽  
pp. 1785
Author(s):  
Igor Medvedev ◽  
Alisa Medvedeva
Keyword(s):  
Baltic Sea ◽  
Sea Level ◽  
Absolute Maximum ◽  
The Baltic Sea ◽  
Sea Level Oscillations ◽  
Gulf Of Riga ◽  
Decadal Variations ◽  
The Baltic ◽  
High Coherence

The present study examines the seasonal and decadal changes of the variance of the synoptic (periods from 2 days to 30 days) and mesoscale (periods from 2 h to 2 days) sea level oscillations in the Baltic Sea. Long-term hourly sea level records were used at 12 tide gauges located in different parts of the sea. We used spectral analysis to estimate the variance for different time scales. The spectral density of sea level oscillations in the Baltic Sea has maximum values in winter when the cyclonic activity in the atmosphere is more intensive. The maximum variances of synoptic σsyn2  and mesoscale σmes2 sea level oscillations are observed in winter, except for the heads of the Gulf of Finland (Gorny Institute) and Gulf of Riga (Pärnu), where the absolute maximum of σsyn2 is reached in November. The variances σsyn2 and σmes2 from November to February are 2–3 and 5 times higher than in the summer. The values of σsyn2 and σmes2 are characterized by high correlation up to 0.7–0.75 with wind variations and atmospheric indices (NAO, AO, and SCAND) in winter and low correlation in summer. The zonal wind and σmes2 in Gorny Institute are characterized by wide areas of high coherence at periods of 0.7–4 years. At Gedser, σsyn2 decreased by 19%, and at Ratan it increased by 17% over 90 years. The values of σmes2 over 90 years increased by 32% at Klagshamn, 36% at Ratan, and up to 60% at Kungsholmsfort.

scholarly journals Survey of Presence of Non-Indigenous Eurytemora Carolleeae in the Gulf of Riga (Baltic Sea) Five Years After its First Discovery

2018 ◽  
Vol 72 (4) ◽  
pp. 230-235
Author(s):  
Labuce Astra ◽  
Ikauniece Anda ◽  
Strāķe Solvita ◽  
Souissi Anissa
Keyword(s):  
Baltic Sea ◽  
Calanoid Copepod ◽  
Reproduction Rate ◽  
Indigenous Species ◽  
Physiological Plasticity ◽  
Eurytemora Affinis ◽  
Male And Female ◽  
Key Species ◽  
Gulf Of Riga ◽  
Non Indigenous Species

Abstract In the brackish ecosystem of the Gulf of Riga, the calanoid copepod Eurytemora affinis is a key species, but recently a new non-indigenous species Eurytemora carolleeae was discovered in the region. In the present study, we aimed to validate the presence of E. carolleeae in the southern part of the Gulf of Riga five years after its first discovery. The study area is the closest region to the Rīga harbour — the main source of non-indigenous species arrival in the Gulf. Recent studies have predicted the possible potential of E. carolleeae invasion due to its physiological plasticity. Male and female specimens of Eurytemora were collected in spring, summer, and autumn of 2013, and analysed based on three morphological indicators. Despite the higher reproduction rate of E. carolleeae, this intrusive species does not seem to have succeeded in establishing during the five-year period after its first discovery in the Gulf of Riga, and hence does not present a threat to the native E. affinis population in the study area.

scholarly journals Non-stationary analysis of water level extremes in Latvian waters, Baltic Sea, during 1961–2018

2021 ◽  
Vol 21 (4) ◽  
pp. 1279-1296
Author(s):  
Nadezhda Kudryavtseva ◽  
Tarmo Soomere ◽  
Rain Männikus
Keyword(s):  
Time Series ◽  
Baltic Sea ◽  
Water Level ◽  
Shape Parameter ◽  
Linear Trend ◽  
Significant Linear Trend ◽  
Gulf Of Riga ◽  
Baltic Proper ◽  
The Baltic ◽  
Eastern Baltic

Abstract. Analysis and prediction of water level extremes in the eastern Baltic Sea are difficult tasks because of the contribution of various drivers to the water level, the presence of outliers in time series, and possibly non-stationarity of the extremes. Non-stationary modeling of extremes was performed to the block maxima of water level derived from the time series at six locations in the Gulf of Riga and one location in the Baltic proper, Baltic Sea, during 1961–2018. Several parameters of the generalized-extreme-value (GEV) distribution of the measured water level maxima both in the Baltic proper and in the interior of the Gulf of Riga exhibit statistically significant changes over these years. The most considerable changes occur to the shape parameter ξ. All stations in the interior of the Gulf of Riga experienced a regime shift: a drastic abrupt drop in the shape parameter from ξ≈0.03±0.02 to ξ≈-0.36±0.04 around 1986 followed by an increase of a similar magnitude around 1990. This means a sudden switch from a Fréchet distribution to a three-parameter Weibull distribution and back. The period of an abrupt shift (1986–1990) in the shape parameters of GEV distribution in the interior of the Gulf of Riga coincides with the significant weakening of correlation between the water level extremes and the North Atlantic Oscillation (NAO). The water level extremes at Kolka at the entrance to the Gulf of Riga reveal a significant linear trend in shape parameter following the ξ≈-0.44+0.01(t-1961) relation. There is evidence of a different course of the water level extremes in the Baltic proper and the interior of the Gulf of Riga. The described changes may lead to greatly different projections for long-term behavior of water level extremes and their return periods based on data from different intervals. Highlights. Water level extremes in the eastern Baltic Sea and the Gulf of Riga are analyzed for 1961–2018. Significant changes in parameters of generalized-extreme-value distribution are identified. Significant linear trend in shape parameter is established at Kolka. The shape parameter changes in a step-like manner. The shape parameter of GEV has regime shifts around 1986 and 1990 in the gulf.

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