Energy content in relation to the population dynamics of Mysis mixta (Lilljeborg) from the Southern Baltic

The energy content of Mysis mixta from the Southern Baltic in relation to its body weight was studied in June, August and October 1986, and April and May 1987. In June, immature animals (4-13 mm) and adult females (18-25 mm) dominated. The same composition was found in August, although the size had changed: the immature animals ranged from 10 to 21 mm and adult females from 21 to 30 mm. A more homogeneous population ranging from 12 to 22 mm was found in October. Males occurred in large numbers only in autumn. The dry weight was 15.04 % of the wet weight, and included 8.18% ash. The relationship between dry weight and body length fitted the power function W = 0.714 L2.835. The average energy content of M. mixta was high: 24.748 Jmg-1 OW and 27.055 Jmg-1 AFDW.There was no significant difference in energy content between adult females and males in October, when both sexes were present. Energy content per dry weight increased with the size of the animals. M. mixta obtained in the study area showed similar energy content to each other

Differences in stress tolerance and brood size between a non-indigenous and an indigenous gammarid in the northern Baltic Sea

Differences in stress tolerance and reproductive traits may drive the competitive hierarchy between nonindigenous and indigenous species and turn the former ones into successful invaders. In the northern Baltic Sea, the non-indigenous Gammarus tigrinus is a recent invader of littoral ecosystems and now occupies comparable ecological niches as the indigenous G. zaddachi. In laboratory experiments on specimens collected between June and August 2009 around Tva¨rminne in southern Finland (59°500N/23°150E), the tolerances towards heat stress and hypoxia were determined for the two species using lethal time, LT50, as response variable. The brood size of the two species was also studied and some observations were made on maturation of juveniles. Gammarus tigrinus was more resistant to hypoxia and survived at higher temperatures than G. zaddachi. Brood size was also greater in G. tigrinus than in G. zaddachi and G. tigrinus matured at a smaller size and earlier than G. zaddachi. Hence, there are clear competitive advantages for the non-indigenous G. tigrinus compared to the indigenous G. zaddachi, and these may be further strengthened through ongoing environmental changes related to increased eutrophication and a warming climate in the Baltic Sea region

Influence of transmembrane pressure and membrane cut-off on yield and ultrafiltration selectivity of model protein concentrate solutions of whey with lactic acid addition

Badano proces ultrafiltracji modelowych roztworów koncentratu białkowego serwatki z dodatkiem kwasu mlekowego. Przeprowadzono analizę wpływu ciśnienia oraz ci/f-p//'membrany na wydajność i selektywność procesu separacji membranowej. Wynika z niej, że z punktu widzenia możliwości zastosowania w bioprocesie wspomaganym membranami do otrzymywania kwasu mlekowego z odpadowej serwatki w procesie ciągłym, lepszą charakterystykę posiada membrana o cut-off 1 kDa w warunkach ciśnienia transmembranowego 0,3 MPa.The ultrafiltration of model protein conccntratc solutions of whey with lactic acid addition was investigated. An influence of pressure and membrane cutoff on yield and selectivity of membrane separation process was analyzed. From a point of view of membrane-supported continuous bioprocess in the production of lactic acid from waste whey, it can be stated that the better characteristic represents the membrane of 1 kDa cut-off at transmembrane pressure of 0.3 MPa

Changes in species composition of the genus Gammarus Fabr. in Puck Bay

This paper describes the current species composition of the genus Gammarus in Puck Bay (western Gulf of Gdańsk, Poland).Sa mples were taken at 9 shallow (ca 0.4 m deep) and 4 deeper (ca 10 m) stations from April 1997 to March 1998. Six Gammarus species were recorded. Gammarus salinus was the most numerous, making up 34.95% of the total of identified amphipod specimens. This species was common throughout the bay but rarely predominant. G. zaddachi (34.75%) was dominant in the northern part of the bay from January to April and was found in almost 2/3 of samples.Less numerous were G. oceanicus (19.15%), common in the southern and eastern parts of Puck Bay, and G. duebeni (9.85%), prevalent in shallow and rocky locations. G. inequicauda and G. locusta made up only 1.13% and 0.12% of the total amphipod material respectively. The species composition of the genus varied considerably not only from one sampling locality to another but also from season to season.I t is possible that two species (G. locusta and G. inequicauda) are currently withdrawing from Puck Bay

The Chinese mitten crab Eriocheir sinensis (Decapoda: Grapsidae) from Polish waters

The Chinese mitten crab Eriocheir sinensis Milne-Edwards, 1854 is a newcomer to the Baltic Sea. Previous studies have shown that since the 1940s single large specimens of this species have been caught annually in Polish waters. The invasion of the Chinese mitten crab has been reported from many European countries, including Poland, where it is especially abundant in the Odra Estuary. Of 186 specimens captured in Lake Dąbie in August 1998, 45% were females and 55% males. The carapace width of these crabs varied between 53 and 88 mm and the average wet weight was 169±45.3 g