Cladoceran remains in lake sediments: a comparison between plankton counts and sediment records

To evaluate the comparability of neo- and paleo-limnology, we made year-to-year as well as seasonal comparisons of contemporary zooplankton data and cladoceran remains in thick (9–42 mm) annual laminations in sediment of Lake Vesijärvi, southern Finland. We calculated the expected annual exuviae production of nine planktonic taxa in the water column using contemporary zooplankton records, and compared the value to the observed net accumulation of their remains in deep sediment for 7 years. Although all of the species studied occur commonly in the lake pelagic zone, deposition of remains differed significantly among taxa. The observed accumulation of three Bosmina species and Chydorus sphaericus was similar to or exceeded expected values, suggesting good preservation of their remains as well as focusing of sediment into the deepest part of the lake. The accumulation of Limnosida and Leptodora remains exceeded expected values several fold, suggesting under-representation of these species in pelagic plankton samples, as well as efficient transportation and spatial averaging of their remains in the sediment. Daphnia, Diaphanosoma, and Ceriodaphnia were clearly under-represented in the sediment due to poor preservation of their remains and use of a 50-μm sieve in sediment processing. Thus, sieving should be taken into account as a possible source of bias. Correlation between relative abundances of all species in the sediment and in the plankton was weak (r _s = 0.54, P < 0.001), but for well-preserved species, the correlation was strong (r _s = 0.91, P < 0.001). Inter-annual variation in the deposition of remains suggested that resuspension and sediment focusing may vary between years, thus making it difficult to interpret absolute abundances, even though the deepest part of the basin shows clear varve formation and seasonality is well recorded. Detailed study of the uppermost lamination showed the seasonal succession of a cladoceran community within an annual varve as well as differences in the seasonality and intensity of ephippia production among the species. We recommend that results of cladoceran analyses be expressed in several ways (relative abundances, per unit dry weight, per unit organic matter, and as net accumulation values) before drawing final conclusions, as each approach may reveal a different aspect of the deposition process. In addition, sedimentation differences between epilimnetic and hypolimnetic species should be considered in stratified lakes.     

Not In The Same World: Topological Youths,Topographical Policies

Public attitudes continue to portray youths in Western societies as being passive and disengaged. Critical scholars are largely unanimous in that the misrecognition of and disrespect for young people's everyday experiences and activities form a major reason why they appear detached from politics and public life. Contributing to this debate, this paper traces the everyday experiences of some Finnish urban youths, and argues that their lived worlds differ notably from the worlds of the public administration that seeks to address youths as active citizens. Based on these findings, the paper proposes the pragmatically oriented concepts of “issue publics” and “topological connectives” for rethinking youth participation and democratic life more broadly.     

Knowledge and Reasoning in Spatial Analysis

Reasoning is an essential part of any analysis process. Especially in visual analytics, the quality of the results depends heavily on the knowledge and reasoning skills of the analyst. In this study, we consider how to make the results transparent by visualizing the reasoning and the knowledge, so that persons from outside can trace and verify them. The focus of this study is in spatial analysis and a case study was carried out on a process of off‐road mobility analysis. In the case study, linked views of a map and a PCP were identified as reasoning artifacts. The knowledge used by the analyst was formed by these artifacts and the tangible pieces of information identified in them, along with the mental models of the analyst′s mind. To make the results transparent, the tangible pieces of information were marked with sketches and the mental models were presented in causal graphs because it was found that causality was central to the reasoning process in the case study. The causal graph allows the reasoning of the analyst to be studied, as well as traced back to its origin.     

A spatial fuzzy influence diagram for modelling spatial objects’ dependencies: a case study on tree-related electric outages

Spatial objects can be interconnected and mutually dependent in complex ways. In Geographical Information Science, spatial objects’ topological relationships are not discussed together with their attributes’ dependencies, and the vagueness of spatial objects is often ignored during the spatial modelling process. To address this, a spatial fuzzy influence diagram (SFID) is introduced. Compared to the traditional statistical or fuzzy modelling approach, the influence diagram brings advantages in helping decision-makers structure complex interdependency problems. A questionnaire was developed to evaluate the applicability of using an influence diagram in modelling spatial objects’ dependencies. As a case study, an SFID is applied to tree-related electric outages. The result of the case study is represented as a vulnerability map of electrical networks. The map shows areas at risk due to tree-related electric outages. The results were first validated by using a visual comparison of the vulnerability map and electricity fault data. In the second validation step, the percentage of fault data, which has received values in different vulnerability categories, was calculated. The results of the case study can be used to support the decision-making process of electrical network maintenance and planning.     

Young people’s voiceless politics in the struggle over urban space

This article discusses the particularity of young people’s politics as it unfolds in the practice of everyday life. By exploring a conflict concerning the use of a public park in the City of Oulu, Finland, we discuss how young people may participate in struggles over urban space trough politics that is not based on voice but voicelessness. This political engagement can be understood as a form of nonparticipatory politics that is easily left unnoticed—politics that shirks civic involvement, customary participatory practices and articulated resistance. We deem it important to acknowledge such action as political for two reasons. First, voiceless politics is a weapon of the weak: It is used when other political agencies are not feasible e. Viewing non-participation as apolitical will only further marginalize those who practice politics in such ways. Second, it is important to find ways of acknowledging nonparticipatory action because, while not commonly understood as politics, it is not easily bypassed in political struggles either. By distinguishing political aspects from young people’s urban behaviors, instead of hearing their presence as mere noise, provides tools for bringing their politics to the public agenda and thus developing more democratic urban spaces.     

Identifying Critical Locations in a Spatial Network with Graph Theory

Effective management of infrastructural networks in the case of a crisis requires a prior analysis of the vulnerability of spatial networks and identification of critical locations where an interdiction would cause damage and disruption. This article presents a mathematical method for modelling the vulnerability risk of network elements which can be used for identification of critical locations in a spatial network. The method combines dual graph modelling with connectivity analysis and topological measures and has been tested on the street network of the Helsinki Metropolitan Area in Finland. Based on the results of this test the vulnerability risk of the network elements was experimentally defined. Further developments are currently under consideration for eventually developing a risk model not only for one but for a group of co‐located spatial networks.     

Development of large shallow Lake Peipsi (North-Eastern Europe) over the Holocene based on the stratigraphy of phosphorus fractions

We studied high-resolution stratigraphy of phosphorus (P) forms in the Holocene sediments of large shallow Lake Peipsi (Estonia/Russia) in order to evaluate the lake ecosystem response to environmental changes and track the lake’s eutrophication history. We distinguished four main periods in the history of Lake Peipsi, each having likely different factors responsible for the distribution pattern of P fractions in the sediment record. We suggest that in the oldest period, from ca. 10.4 up to 7.3 cal ka BP, the sediment composition was mainly determined by rising water level, the second period dated 7.3–2.3 cal ka BP was governed mainly by stable hydrology and P loading, while the third period between 2.3 and 0 cal ka BP was primarily influenced by emerging anthropogenic impact. The sediments from the last period since 1950 are subject of ongoing diagenetic processes but still reflect rapid eutrophication of the lake. Comparison of the results with periods derived from other sediment proxies proved the usability of P fractions stratigraphy in reconstruction of the development of lakes.     

Spatio‐temporal patterns of major ions in urban stormwater under cold climate

Multiple natural and anthropogenic factors affect urban water chemistry. However, little is known about the abundance or temporal variation of major ions in urban runoff. This study explores the spatio‐temporal variation of major dissolved ions (Na, K, Ca, Mg, Cl, NO₃, and SO₄) and total dissolved solids (TDS) in cold climate urban stormwater. Three watersheds with varying degrees of urban land use intensity and imperviousness (from 36% to 66%) in Helsinki, Finland, were continuously monitored for 5 years using an automated sampling procedure to obtain stormwater discharge and ion concentrations and, thus, loadings. High‐resolution datasets, including long‐term continuous discharge, both measured and simulated (using Storm Water Management Model), and automatic water quality sampling enabled the accurate calculation of loads of ions and TDS. Water quality was related to explanatory watershed characteristics (e.g., watershed physiography and sampling time) using hierarchical clustering, nonmetric multidimensional scaling, and hierarchical partitioning methods. Urban land use contributed to increased ion concentrations and loads year‐round. This study highlights how stormwater ion concentrations are elevated across seasons, indicating chronic pollution phenomena. The greatest loads occurred during summer (except for Na and Cl), while the highest variation in loads was observed in autumn. Significant clusters among ions were found in the hierarchical cluster analysis, suggesting similar temporal patterns and sources for the ions in each cluster. The importance of land use was evident, though in the most urbanized watershed, concentrations were not linked to any of the investigated watershed characteristics. Based on our results, only Na and Cl are manageable by alternative winter road antiskid practices, whereas other ions resulted from diffuse pollution sources, being therefore more difficult to control. Finally, this study contributes to an increased understanding of the temporal and spatial patterns of ions in stormwater and highlights the need for consistent time series data for ion monitoring under cold climatic conditions in order to enable reliable estimates of their loads to adjacent water bodies. Finally, year‐round stormwater treatment is highly recommended.     

Simulation of green roof test bed runoff

Low Impact Development (LID) aims to mitigate the hydrological impacts of urbanization by replication of processes in natural catchments. Green roofs covered with vegetation and pervious substrate are one alternative among a wide range of LID tools. Water retention of green roofs depends on many factors (e.g. local climate), and measurements remain crucial in evaluating their performance. The simulation of green roof retention by a hydrological model is one option to evaluate their potential benefits before implementation. In this paper, we evaluated the ability of the recently introduced LID green roof module of the stormwater management model to replicate runoff from monitored green roof test beds under Nordic climate conditions. A parameter sensitivity analysis was conducted to identify calibration parameters. The model showed an overall acceptable performance, and the results indicated the importance of accurately estimating potential evapotranspiration rates for inter‐event periods, which is essential in representing the retention capacity regeneration. Copyright © 2015 John Wiley & Sons, Ltd.