The unfulfilled promise of urban Lake Kleine Melanen (The Netherlands): Diagnostics, experiment on reduction of sediment P-release and in-lake restoration

Figures & data

Figure 1. Location of Lake Kleine Melanen in The Netherlands (left) and detailed map of the lake (right). 1 = sampling location 1993–2008, 2 = sampling location 2009–2014, 3 = location of outlet weir, 4 = locations of the enclosure experiment.

Table 1. Characteristics of Lake Kleine Melanen before restoration (situation in 2009; TP and Chl-a are the mean concentrations for the period 2008–2009, samples taken at water depth 30 cm).

Longitude/latitude	N 51°30′44″, E 4°17′33″
Area (ha)	4
Water residence time	2 months
Mean water depth (m)	1.0
Sediment	1 m mud on peat
Cover submerged macrophytes (%)	0
Fish biomass (kg/ha)	605 (67% carp)
TP (mg/L)	0.31 (SD 0.14, n = 20)
Chl-a (µg/L)	107 (SD 120, n = 16)
Cyanobacterial Chl-a (µg/L)^1	52 (SD 122, n = 14)

¹ Mean concentration for period August 2007–July 2010.

Table 2. Restoration measures, date of implementation and details. LMB = lanthanum modified bentonite.

Measure	Implementation	Details
Fish removal	Sep 2010	Electrofishing of shorelines, trawl fishing of open water. Fish removal was 75% (including the winter fish kill of Feb 2010). Remaining fish biomass 152 kg/ha (including all species originally present with low biomass of remaining carp).
Dredging	Nov 2010–May 2011	Thickness soft sediment before dredging was on average 0.93 m. In 3.5 ha, 0.64 cm soft sediment was removed by cutter dredger and crane. In 0.5 ha, soft sediment (1.30 m thickness in this area) was completely removed down to underlying peat.
Removal of trees and shrubs	Oct–Nov 2011	Trees and shrubs on shorelines pruned and some felled to reduce P load by litter fall and provide more light on shorelines. Branches hanging over open water were removed.
Construction of marsh area	Dec 2011–Feb 2012	Removal of wooden shoreline protection and construction of natural shorelines covering 20% of lake area (inclination of slopes 1:15). No planting or seeding on shorelines.
Sand capping and LMB	Aug–Oct 2012	20 cm thick clean sand layer (D50 > 250 µm, ≤5% weight of particles <65 µm) and 414 g LMB/m^2 (20.7 g La/m^2) in the lowest 5 cm of the sand cap.

Table 3. External P loads (mg P/m²/d) of Lake Kleine Melanen before restoration (see Supplement for details).

	P load (mg P/m^2/d)
Separated sewer system	6.5
Deposition on lake	0.2
Water birds	0.2
Feeding of water birds	0.1
Litter fall	0.3
Bait angling	0.1
Dog feces and urine	0.1
Total	7.5

Table 4. Sediment characteristics (density, % dry matter, % organic matter) and concentrations of total phosphorus (TP), iron (Fe), and sulfur (S) in sediment (A; g/kg DW) and pore water (B; mg/L). DW = dry weight, SE in parentheses (data extracted from Waltjé et al. 2009).

A				g/kg DW
	Density (kg/L)	Dry matter (%)	Organic matter (% of DW)	TP	Fe	S
Soft sediment (depth 0.0–0.1 m)	1.04	9.5 (2.5)	47.9 (3.3)	1.8 (0.3)	23.1 (3.6)	20.4 (3.2)
Peat (mean depth 1.0–1.1 m)	1.33	25.1 (10.1)	64.5 (15.8)	0.16 (0.03)	1.5 (0.3)	3.9 (1.0)

B	mg/L
	TP	Fe	S
Soft sediment (depth 0.0–0.1 m)	5.05 (0.35)	7.28 (0.76)	0.52 (0.01)
Peat (mean depth 1.0–1.1 m)	0.87 (0.10)	0.19 (0.08)	0.73 (0.30)

Figure 2. Total phosphorus (TP) concentrations (mg/L) in enclosure experiment. Treatments: C (control, panel A), S (sand capping, panel B), SL (sand capping + LMB, panel C), SLP (sand capping + LMB + PAC, panel D). The gray areas indicate the TP concentration in the lake (days −11 to 87). Open symbols indicate the TP concentration on day −4, at 1.5 h after sand addition. Error bars indicate 1 SE (n = 3). In panel B the course of TP in each replicate is presented.

Figure 3. Ortho-phosphate (OP) concentrations (mg/L) in enclosure experiment. Treatments: C (control, panel A), S (sand capping, panel B), SL (sand capping + LMB, panel C), SLP (sand capping + LMB + PAC, panel D). The gray areas indicate the OP concentration in the lake (days −11 to 87). Open symbols indicate the OP concentration on day −4, at 1.5 h after sand addition. Error bars indicate 1 SE (n = 3). In panel B the course of OP in each replicate is presented.

Table 5. Enclosure experiment: median concentrations of total phosphorus (TP, mg/L), ortho-phosphate (OP, mg/L), total nitrogen (TN, mg/L), total and cyanobacterial Chl-a (µg/L), total and filterable lanthanum (TLa, FLa, µg/L) and median turbidity (FTU, Formazin Turbidity Units) in control (C; n = 3) enclosures and in enclosures with sand capping (S; n = 2), sand capping + LMB (SL; n = 3), and sand capping + LMB + PAC (SLP; n = 3) during the 87 d experimental period. SE in parentheses except for OP. For OP, the number of sampling events with a mean concentration <0.01 mg P/L is given in parentheses (total number of sampling events = 8). The right column shows the results of nonparametric Kruskal–Wallis Test. Capital letters (A, B, C) indicate significantly different groups (P < 0.05).

	Control (C)	Sand (S)	Sand + LMB (SL)	Sand + LMB + PAC (SLP)
TP (mg P/L)	0.22^A (0.06)	0.14^AB (0.03)	0.12^B (0.02)	0.07^C (0.01)	χ^2(3) = 42.144 P < 0.0005
OP (mg P/L)	0.01 (3)	0.01 (4)	0.01 (6)	0.01 (7)
TN (mg N/L)	3.50^A (0.19)	1.95^B (0.20)	1.95^B (0.10)	1.75^B (0.11)	χ^2(3) = 48.006 P < 0.0005
Total Chl-a (µg/L)	121.8^A (19.4)	20.5^BC (14.4)	13.9^B (11.0)	6.6^C (1.7)	χ^2(3) = 31.462 P < 0.0005
Cyanobacterial Chl-a (µg/L)	10.0^A (3.0)	2.0^AB (2.2)	1.2^AB (1.6)	0.1^B (0.2)	χ^2(3) = 16.912 P = 0.001
Turbidity (FTU)	11.0^A (1.3)	14.5^A (11.3)	18.5^A (10.5)	2.6^B (0.5)	χ^2(3) = 22.399 P < 0.0005
TLa (µg/L)	<12.0^A (0)	<12.0^A (0)	1327.5^B (276.8)	292.5^B (61.0)	χ^2(3) = 75.895 P < 0.0005
FLa (µg/L)	<12.0^A (0)	<12.0^A (0)	67.3^B (14.0)	21.4^B (4.5)	χ^2(3) = 61.106 P < 0.0005

Figure 4. Concentrations of total Chl-a (µg/L, open symbols) and cyanobacterial Chl-a (µg/L, filled symbols) in enclosure experiment. Treatments: C (control, panel A), S (sand capping, panel B), SL (sand capping + LMB, panel C), SLP (sand capping + LMB + PAC, panel D). The gray areas indicate the total Chl-a concentration and the hatched areas indicate the cyanobacterial Chl-a concentration in the lake (days −11 to 87). Symbols at day −4 indicate the Chl-a concentrations 1.5 h after sand addition. Error bars indicate 1 SE (n = 3). In panel B the course of total and cyanobacterial Chl-a in each replicate is presented.

Table 6. Whole-lake measures: mean concentrations of total phosphorus (TP, mg/L), ortho-phosphate (OP, mg/L), total nitrogen (TN, mg/L), chlorophyll a (Chl-a, µg/L), cyanobacterial chlorophyll a (cyano Chl-a, µg/L), total and filterable lanthanum (TLa, FLa, µg/L), oxygen (O₂, mg/L), and mean Secchi disk transparency (SDT, m) in Lake Kleine Melanen before (Jan 2008–Aug 2010), during (Sep 2010–Oct 2012), and after (Nov 2012–Oct 2014) measures were implemented, based on monthly sampling except cyano Chl-a, TLa, and FLa. SE in parentheses.

	Before measures	During measures	After measures
TP (mg P/L)*	0.30 (0.02)	0.30 (0.04)	0.11 (0.01)
OP (mg P/L)*	0.10 (0.02)	0.04 (0.01)	0.01 (0.00)
TN (mg N/L)	2.30 (0.10)	2.79 (0.30)	1.95 (0.11)
Chl-a (µg/L)*	111 (20)	74 (11)	39 (5)
Cyano Chl-a (µg/L)^1	51.6 (32.6)	n.a.	5.9 (1.9)
SDT (m)	0.54 (0.03)	0.47 (0.06)	0.61 (0.05)
TLa (µg/L)^2	< 0.2	434.8 (130.4)	38.1 (6.0)
FLa (µg/L)^2	< 0.02	23.06 (5.57)	6.68 (1.15)
O2 (mg/L)	9.9 (0.8)	9.0 (0.5)	9.6 (0.4)

¹ Measurements before measures (n = 14) on 3 August 2007, 6 August 2008, 6 August 2009, 25 February 2010–30 July 2010, and after measures (n = 26); n.a. = not available.

² Measurements before LMB application on 15 August 2012 (n = 1), during LMB application (n = 8), and after LMB application (n = 21).

* Significant difference before and after measures (P < 0.05).

Waltjé E, Haverkamp S, Steketee J. 2009. Waterbodemonderzoek Groote en Kleine Melanen en Ganzenvijvers. [Sediment research Groote and Kleine Melanen and Ganzenvijvers. In Dutch.] Eindhoven, The Netherlands: Tauw bv Consultancy.

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