Suomenlinnan Kustaanmiekan ketokasvillisuus ja siihen vaikuttavat tekijät

Suomenlinna on yksi Helsingin suosituimmista matkailu- ja kulttuurinähtävyyksistä. Kustaanmiekan, samoin kuin koko Suomenlinnan luonto on muodostunut perinteisestä suomalaisesta saaristoluonnosta ja vuosisatojen saatossa paikalle tulleista linnoituksien kasvistosta. Saaren vaihtelevien elinympäristöjen johdosta alueen kasvillisuus on hyvin rikasta. Linnoituksien monet kasvilajit ovat tulleet tulokaskasveina eri puolilta Eurooppaa sekä Venäjältä. Suurin osa Suomenlinnan alueesta on kallioketoa ja tämän lisäksi myös valliketoa, joista molemmat kuuluvat suojeltaviin alueisiin. Kustaanmiekan niityillä kasvaa keto- ja paahdelajeja, kuten harvinaista ketonoidanlukkoa (Botrychium lunaria L.) sekä ketoneilikkaa (Dianthus deltoides L.). Tämän tutkimuksen ensisijaisena tarkoituksena oli kartoittaa Kustaanmiekan alueen kesäkauden 2009 ketokasvilajisto ja eri putkilokasvilajien runsaus. Tutkimuksessa selvitettiin myös maaperätekijöiden ja alueen hoitohistorian mahdollista vaikutusta ketokasvilajistoon. Tutkimuksessa kartoitettiin kymmenen eri kedon kasvillisuus Suomenlinnan Kustaanmiekan linnoitusalueella. Kedot sijaitsivat eri puolilla Kustaanmiekkaa, sellaisilla paikoilla, missä ketokasvillisuus oli runsainta. Maastotyöt suoritettiin kesä- ja heinäkuussa laskemalla jokaisen kedon ruutujen putkilokasvien peittävyydet sekä listaamalla ylös myös ruutujen ulkopuoliset kevät- ja loppukesän kukkijat touko- ja elokuussa. Maaperän ominaisuuksien määrittämiseksi otettiin kultakin kedolta pintamaanäytteet elokuussa. Muita tutkittuja muuttujia olivat maapinnan kaltevuus sekä sammalen, karikkeen, paljaan maan, kenttäkasvillisuuden pohjakerros ja kallion osuus tutkimusruuduilla. Ketojen kasvillisuuden keskimääräinen korkeus mitattiin kesä- ja heinäkuussa. Kasvistossa oli selviä eroavaisuuksia ketojen välillä. Kasvilajien määrä vaihteli ketojen kokonaislajimäärän ollessa 40-60 kasvilajia. Yhteensä kedoilta löytyi 120 eri putkilokasvilajia, joista useimmat kukkivat sekä kesä- että heinäkuussa. Ketojen kasvilajimäärä vaihteli yhdellä neliömetrillä 6,3-13,6 kasvilajiin, minkä lisäksi Shannon-Wienerin diversiteetti-indeksi vaihteli 1,4-2,3 arvon välillä. Yleisimpiä lajeja, joita kedoilla tavattiin, olivat muun muassa siankärsämö (Achillea millefolium L.), koiranheinä (Dactylis glomerata L.), juolavehnä (Elymus repens L.) ja hopeahanhikki (Potentilla argentea L.). Alueella kasvoi myös muutamia sotatulokaslajeja kuten harmiota (Berteroa incana L.), ukonpalkoa (Bunias orientalis L.) ja karvahorsmaa (Epilobium hirsutum L.). Maaperätekijöillä, kuten suurella fosforin pitoisuudella ei ollut vaikutusta kasvilajien määrään kedoilla. Vain maan pH ja johtoluku korreloivat positiivisesti ketojen kasvillisuuden korkeuden kanssa. Vaikka tulosten perusteella ketojen hoidolla ei ollut vaikutusta ketojen kasvillisuuden määrään, voidaan kuitenkin olettaa oikeanlaisen hoidon parantavan tyypillisten ketokasvien kilpailukykyä muita niittykasveja kohtaan.

Fast- and drift-ice communities in the Bothnian Bay and the impact of UVA radiation on the Baltic Sea ice ecology

The aim of this thesis was to study ecology of Baltic Sea ice from two perspectives. In the first two studies, sea-ice ecology from riverine-influenced fast ice to drift ice in the Bothnian Bay was investigated, whereas the last two studies focus on the sensitivity of sea-ice bacteria and algae to UVA examined in situ. The seasonal sea ice cover is one of the main characteristics of the Baltic Sea, and despite the brackish parental water, the ice structure is similar to polar ice with saline brine inclusions, the sea ice habitat. The decreasing seawater salinity from the northern Baltic Sea to the Bothnian Bay translates to decreasing brine volumes along the gradient, governing the size and community structure of the food webs in ice. However, the drift and fast ice in the Bothnian Bay may differ greatly in this sense, as drift ice may have been formed at more southern locations. Rafting and the formation of snow ice are common processes in the ice field of the Bothnian Bay. As evidenced in this thesis, rafting altered the vertical distribution of organisms and snow-ice formation provided habitable space in the better-illuminated, nitrogen-rich surface layer. The divergence between fast and drift ice became apparent at the more advanced stages, and chlorophyte biomass decreased from fast to drift ice, while the opposite held true for protozoan and metazoan biomass. The brine volumes affected the communities somewhat, and a higher percentage of flagellate species was generally linked to lower brine volumes, whereas chain-forming diatoms were mostly concentrated in layers with larger brine volumes. These results add to knowledge of the ecological significance of the ice cover lasting up to 7 months per year in this area. Sea-ice food webs are generally light-limited, but while increasing light irradiances typically enhance the primary production and further, the secondary production in sea ice, any increase in solar radiation also includes an increase in harmful UVA radiation. The Baltic Sea ice microbial communities were clearly sensitive to UVA and the responses were strongly linked to the earlier light history, as well as to the solar irradiances they were exposed to. The increased biomass of chlorophytes and pennate diatoms, when UVA was excluded, indicates that their normally minor contribution to the biomass in the upper layers of sea ice might be partly dictated by UVA. The effects of UVA on bacterial production in Baltic Sea ice mostly followed the responses in algal growth, but occasionally the exposure to UVA even enhanced the bacterial production. The dominant bacterial class, Flavobacteria, seemed to be UVA-tolerant, whereas all the Alpha-, Beta- and Gammaproteobacteria present in the surface layer showed UVA sensitivity. These results indicate that changes in the light field of ice may alter the community structure and affect the functioning of ice food webs, and are of importance when the effects of thinning of the ice cover are assessed.

Behavioural responses to anthropogenic disturbances

When a habitat undergoes change, the first response of an individual is often behavioural adjustment. This immediate response can determine whether the population will survive or not, as behavioural flexibility gives time for genetic changes to arise later on. Habitat changes that alter reproductive behaviours can have long-lasting effects on populations. If the selective regime has changed under the new conditions, mate choice cues may no longer reliably reflect an individual s quality. Thus, animals have to be able to adjust their reproductive behaviours to the local conditions. The aim of my thesis was to discuss if and how animals are able to respond to rapid anthropogenic environmental change, and to study the mechanisms of the responses and the evolutionary consequences. The main focus was on the effects of human-induced eutrophication on the reproductive behaviour of fishes. Eutrophication is the result of increased nutrient input and can cause dense underwater vegetation and algal blooms. I used fishes from two very different ecosystems as model species, the Baltic Sea threespine stickleback (Gasterosteus aculeatus) and the desert goby (Chlamydogobius eremius), an endemic species of the Lake Eyre region in Central Australia. I investigated the effects of increased habitat complexity on courtship behaviour and the possibility of local differentiation in courtship and nest building behaviour depending on the level eutrophication in the habitat of origin. Furthermore, I observed the effect of turbidity on stickleback nest building behaviour. The results show that threespine stickleback males, which were born in areas that have been eutrophied for decades, court females at a higher intensity than males from clear water areas. Similarly, male desert gobies increased their courtship effort in dense vegetation. Intense courtship could be an adjustment to reduced visibility and lowered predation risk in the densely vegetated sites. However, there were no clear differences in nest building between males from clear and eutrophied areas under standardized conditions. This was expected as Baltic Sea sticklebacks prefer to nest under vegetation cover and are fairly rigid in adjusting their nest characteristics. Nest building was affected by increased turbidity: males built smaller nests with a larger nest entrance in turbid water. The large variation in the magnitude of phytoplankton blooms may require a rapid adjustment of the optimal nest structure to the current conditions. This thesis highlights the complex interactions that are set- off by human-induced changes in habitats and are followed by the immediate behavioural responses. It also encourages more research to tease apart the phenotypic and genetic components of the observed behavioural differences.