Periphyton growth as an indicator of eutrophication; an experimental approach

Growth of periphyton was studied in the Archipelago Sea (Finland) during summer 1994 as a part of the annual monitoring control of fish farms. Experimental growth plates (Whatman GF/C filters) were incubated (two weeks) at 213 sites in different parts of the Archipelago Sea and in the coastal area north of the Archipelago Sea. At each site incubations were repeated two or three times during the summer (July 4- -September 1). The growth of periphyton was measured as the amount of chlorophyll a (mg m-2) extracted from the incubation plates. The growth varied significantly among different parts of the study area. The strongest growth was observed in the inner archipelago and in areas with high fish production and relatively slow water exchange. In the outer archipelago, rapid water exchange ensured good mixing of nutrients from fish farms and other sources into relatively large water volumes. The local impacts of nutrient loading thus remained too low to be detected by measuring nutrient concentrations or periphyton growth. Periphyton growth was positively correlated with concentrations of total nitrogen, total phosphorus and chlorophyll a in the productivity layer (approximately 2 × Secchi depth). A significant inverse correlation was also shown between periphyton growth and Secchi depth. Archipelago areas with different levels of eutrophication could satisfactorily be distinguished in this study. The results were consequent with previous classifications of the eutrophication levels in the Archipelago Sea. Periphyton studies thus are a useful addition to conventional monitoring programs. This revised version was published online in July 2006 with corrections to the Cover Date.     

Quallen an Nord‐ und Ostseeküste

Jellyfishes in the North and the Baltic Sea Jellyfish masses are not only a nuisance for bathers but have significant negative effects on marine ecosystems and economy. The causes of worldwide increasing jellyfish mass occurrences are not fully understood until today. Anthropogenic influences as submarine constructions, overfishing, eutrophication and climate warming are assumed as possible causes. Jellyfish and their relatives have fascinating capabilities and features, including their amazing regeneration potential, a high adaptability on changing environments and especially their weapons, the stinging capsules. Despite the simplicity of their nervous system jellyfish have astonishing perception senses.     

Development of an STS map of an interspecific progeny of <Emphasis Type="Italic">Malus</Emphasis>

Simple sequence repeat (SSR) markers developed from Malus, as well as Prunus, Pyrus and Sorbus, and some other sequence-tagged site (STS) loci were analysed in an interspecific F₁ apple progeny from the cross ‘Fiesta’ × ‘Totem’ that segregated for several agronomic characters. A linkage map was constructed using 259 STS loci (247 SSRs, four SCARs and eight known-function genes) and five genes for agronomic traits—scab resistance (Vf), mildew resistance (Pl-2), columnar growth habit (Co), red tissues (Rt) and green flesh background colour (Gfc). Ninety SSR loci and three genes (ETR1, Rt and Gfc) were mapped for the first time in apple. The transferability of markers from other Maloideae to Malus was found to be around 44%. The loci are spread across 17 linkage groups, corresponding to the basic chromosome number of Malus and cover 1,208 cM, approximately 85% of the estimated length of the apple genome. Interestingly, we have extended the top of LG15 with eight markers covering 25 cM. The average map density is 4.7 cM per marker; however, marker density varies greatly between linkage groups, from 2.5 in LG14 to 8.9 in LG7, with some areas of the genome still in need of further STS markers for saturation.