Zooplankton Diversity and Dispersal by Birds; Insights From Different Geographical Scales

Abstract

Given the major ecological and evolutionary role of dispersal abilities for organisms, as well as the current interest in species' potential for further migration and colonization as a result of climatic changes or human-mediated invasions, our knowledge about dispersal abilities on spatial and temporal scales in many taxa is surprisingly limited. Zooplankton inhabit lakes and ponds that functionally are "aquatic islands" in the landscape, and both community composition and richness depend on their ability to disperse, and their post-dispersal colonization abilities. We here assess the diversity and dispersal of freshwater microcrustaceans based on three types of data; (1) > 2000 lakes on mainland Norway spanning a wide range in longitude, latitude and altitude, (2) a more limited number of ponds at Svalbard that are differently affected by migrating birds, and (3) immigration and colonization of recently constructed wetlands and man-made ponds. At all scales we discuss whether observed patterns in diversity can be explicitly linked to birds as vectors, or if confounding factors such as climate, productivity, age of locality-or other means of immigration, precludes conclusive evidence. The spatial patterns of zooplankton distribution strongly suggest that local sorting is a major determinant of richness and community composition. This sorting may not necessarily lead to similar community composition (the "quorum effect") however. Despite the fact that rapid colonization occurs at local scales, and that birds undoubtedly can transmit animals or resting stages, their role in modulating community structure and richness is still an unsettled issue due to the many confounding parameters. The fact that birds often play a dual role in shaping diversity and community composition, first by direct dispersal, and secondly via affecting post-dispersal species sorting by changing water quality and productivity, is an important aspect of zoochory. Direct experimental evidence (colonization with and without bird exclusion), or genetic analysis of zooplankton species along migration routes, would however be the only ways to establish firm evidence for this case of zoochory.

Can dispersal buffer against salinity‐driven zooplankton community change in Great Plains' lakes?

“…For example, the lake on which we ran our experiment (Kenosee Lake) lacks stream connections except at high water levels (Vance et al, 1997), making direct dispersal unlikely during droughts. However, it may receive dispersers transported by terrestrial animals and waterfowl that travel among the dozens of prairie pothole lakes located within 5 km of its shoreline (Hessen et al, 2019;Vanschoenwinkel et al, 2008b;Frisch et al, 2007). We speculate that the level of dispersal among these types of prairie lakes are probably comparable to that among rock pools in Churchill,…”

“…When simulating dispersal during our enclosure experiments, we selected a dispersal rate of c. 1% of the resident community abundance per day based on studies of an interconnected pond system (Michels et al, 2001) and our desire to test our hypotheses within a reasonable time frame (6-week experiment). However, it may receive dispersers transported by terrestrial animals and waterfowl that travel among the dozens of prairie pothole lakes located within 5 km of its shoreline (Hessen et al, 2019;Vanschoenwinkel et al, 2008b;Frisch et al, 2007). For example, the lake on which we ran our experiment (Kenosee Lake) lacks stream connections except at high water levels (Vance et al, 1997), making direct dispersal unlikely during droughts.…”

Experimental tests of water chemistry response to ornithological eutrophication: biological implications in Arctic freshwaters

“…For the comparison of faecal loading rate and the subsequent effects on water chemistry at a landscape scale, we report previously unpublished chlorophyll a values from a large-scale survey of lakes across Southampton Island (for sampling details, see Mariash et al, 2018; Table 3). Water samples from these lakes were filtered onto GF/F fil-H. L. Mariash et al: Experimental tests of water chemistry response to ornithological eutrophication ters (in duplicates), frozen at −80 • C, and later analyzed using a Cary Eclipse fluorescence spectrophotometer (Aglilent, Santa Clara, USA) using standardized extraction methods and calculations (Holm-Hansen and Riemann, 1978;Jeffrey et al, 1997).…”

“…Biovolume estimates were based on geometrical models and cell measurements using photography and the AxioVision software (Zeiss, Germany) and converted using carbon to volume relationships (Menden-Deuer and Lessard, 2000). Phytoplankton taxonomy relied on the following literature: Cox (1996), Hillebrand et al (1999); John et al (2002), Komárek and Anagnostidis (2000), Guiry and Guiry (2017), Taylor et al (2007), and Wehr et al (2015). Taxa were identified to the genus level when possible but later grouped by class for comparisons.…”

“…While it has been demonstrated that goose droppings are a significant source of total nitrogen (N) and phosphorus (P) for nearby ponds (Côté et al, 2010;Mariash et al, 2018;Olson et al, 2005), only a few studies have attempted to quantify the magnitude of ornithological nutrient loading (Liu et al, 2014;Post et al, 1998) and relate increased nutrients to broader limnological affects (Van Geest et al, 2007;MacDonald et al, 2015;Unckless and Makarewicz, 2007). Birds can also act as vectors for the dispersal of plants, phytoplankton, and zooplankton when propagules are spread through their faeces (Figuerola and Green, 2002;Hessen et al, 2019). Currently, almost no measurements of these broader ecosystem-level effects exist for Arctic ponds.…”