Ecosystem functions of confined-scale artificial tidal flats in urban areas in Japan: analysis of driving factors for function-based design

Figures & data

Figure 1. Location of the two artificial tidal flats where research was conducted in Tokyo Bay: Shiosai Nagisa and Kawasaki Hama, denoted in the figure as SN and KH, respectively

Figure 2. Photos and monitoring stations at (a) Shiosai Nagisa and (b) Kawasaki Hama, and cross-sectional structure of (c) Shiosai Nagisa and (d) Kawasaki Hama. Photograph of (b) was downloaded from the Geospatial Information Authority of Japan (https://mapps.gsi.go.jp/)

Table 1. Definition of ecosystem functions and their indices. The reference indicates the 100-point value of ecosystem functions

Category	Service	Function	Index	Unit of index	Reference value
Provisioning	Food provision	Fisheries resource abundance	Population of manila clam (shell length >20 mm)	population/m^2	1349
Regulating	Water purification	Organic matter consumption	Chemical Oxygen Demand purification flux with benthos	g-COD/m^2/year	502
	Carbon storage	Sediment carbon accumulation	Ignition loss	%	9.3
Cultural	Tourism	Scenery	Brightness with standard soil chart	-	5
	Recreation	Walkability	Median particle diameter	mm	0.075–2
Supporting	Life cycle maintenance	Biodiversity	Species richness of benthos	number/0.186 m^2	43
	Primary production	Microalgae abundance	Sediment chlorophyll-a	μg /cm^2	78

Table 2. Mean value of the water quality at Shiosai Nagisa (SN) and Kawasaki Hama (KH) during survey period (FY 2014 to FY 2017). The value in parentheses indicates the minimum value – maximum value

Site	W. Temperature (°C)	Salinity (psu)	DO (mg/L)	Chl-F (μg/L)
SN	19.8 (6.4–33.6)	27.5 (6.5–35.8)	7.8 (0.1–22.0)	5.9 (0.1–98.2)
HK	21.8 (13.2–30.0)	28.6 (23.5–31.5)	7.6 (5.3–12.3)	5.6 (0.5–31.0)

Figure 3. Continuous measurement data of water qualities at St. SNW in (FY 2014): (a) Water temperature, (b) Salinity, (c) Dissolved oxygen, and (d) Chlorophyll Fluorescence

Table 3. Mean value of the sediment quality at Shiosai Nagisa (SN) and Kawasaki Hama (HK) during survey period (FY 2014 to FY 2017). The value in parentheses indicates the minimum value – maximum value

Site	Station	Grain size (%)			Ignition loss (%)	Sediment brightness
		Gravel (2–75 mm)	Sand (0.075–2 mm)	silt/clay (< 0.075 mm)
SN	SN1.0S	1.6 (0.0–11.0)	98.8 (81.0–98.0)	2.7 (1.0–8.0)	1.3 (1.0–1.4)	2.7 (2–4)
	SN0.5S	4.1 (0.0–19.0)	91.8 (74.0–97.0)	4.1 (2.0–10.0)	1.4 (1.1–1.7)	2.8 (2–5)
	SN0.5 F	1.4 (0.0–6.0)	92.2 (86.0–97.0)	6.4 (2.0–14.0)	2.5 (1.6–3.2)	2.3 (1.5–3)
	SN0.5 G	89.1 (70.0–99.0)	8.5 (1.0–27.0)	2.2 (0.0–4.0)	6.8 (3.6–9.3)	3.0 (2–4)
	SN0.0S	14.1 (6.0–38.0)	78.9 (66.0–69.0)	6.7 (2.0–14.0)	2.6 (1.4–4.2)	2.8 (1.5–4)
HK	HK0.5S	21.9 (4.0–33.0)	76.9 (66.0–96.0)	1.2 (0.0–2.0)	1.1 (0.8–1.3)	3.0 (2–5)
	HK0.0S	25.9 (2.0–49.0)	68.4 (41.0–97.0)	5.7 (1.0–20.0)	1.7 (1.1–3.4)	2.5 (2–3)

Figure 4. Temporal variations of the species richness of benthos, wet weight of benthos, and chlorophyll-a on sediments at each station in Shiosai Nagisa and Kawasaki Hama

Figure 5. Annual mean scores of ecosystem functions at each station in Shiosai Nagisa and Kawasaki Hama. Each Ecosystem function were evaluated using define in Table 1. The names of some ecosystem functions are abbreviations as below, Fisheries: Fisheries resource abundance, Organic matter: Organic matter consumption, Carbon: Sediment carbon accumulation and Microalgae: Microalgae abundance

Table 4. Estimated coefficients of each ecosystem function model using the hierarchical Bayesian model. The value in parentheses indicates the 95% credible interval. The values in bold font indicates the coefficient that does not include zero in the 95% credible interval

	Fisheries resource abundance	Organic matter consumption	Sediment carbon accumulation	Scenery	Walkability	Biodiversity	Microalgae abundance
Intercept	−0.59 (−2.61–1.42)	1.54 (1.06–2.03)	2.91 (2.82–3.00)	4.02 (3.93–4.12)	4.60 (4.59–4.61)	3.54 (3.40–3.68)	2.26 (1.85–2.67)
Temperature	−2.32 (−4.70–0.11)	−0.75 (−1.35 – −0.18)	−0.03 (−0.13–0.08)	−0.03 (−0.14–0.08)	0.00 (−0.02–0.01)	−0.37 (−0.54 – −0.20)	0.58 (0.10–1.07)
Salinity	0.64 (−2.08–0.78)	−0.01 (−0.35–0.34)	−0.04 (−0.10–0.02)	−0.01 (−0.07–0.06)	0.00 (−0.01–0.00)	−0.06 (−0.16–0.04)	0.17 (−0.12–0.45)
DO	−1.20 (−3.06–0.70)	−0.51 (−0.96 – −0.06)	−0.02 (−0.11–0.06)	0.01 (−0.08–0.09)	−0.01 (−0.02–0.00)	−0.16 (−0.29–0.00)	0.32 (−0.06–0.69)
W-Chl-F	2.21 (0.22–4.13)	0.62 (0.15–1.09)	0.02 (−0.06–0.11)	−0.02 (−011 – 0.07)	0.00 (−0.01–0.01)	0.23 (0.10–0.37)	−0.29 (−0.69–0.10)
Ground height	−1.53 (−2.89 – −0.19)	−0.71 (−1.03 – −0.38)	−0.22 (−0.27 – −0.16)	−0.01 (−0.07–0.05)	0.00 (−0.01–0.01)	−0.27 (−0.36 – −0.17)	0.19 (−0.46–0.08)
Slope	−1.57 (−3.44–0.35)	−0.70 (−1.03 – −0.38)	0.00 (−0.08 – −0.08)	0.12 (0.04–0.21)	0.00 (−0.01–0.01)	−0.38 (−0.51 – −0.26)	−0.59 (−0.95 – −0.22)
Material (FNS:Sand)	−1.39 (−5.38–2.57)	−0.82 (−1.86–0.23)	0.39 (0.21–0.57)	−0.21 (−0.40 – −0.02)	0.01 (−0.02–0.03)	0.19 (−0.10–0.50)	0.77 (−0.06–1.61)
Material (GCA:Sand)	−3.50 (−7.63–0.61)	−0.65 (−1.67–0.36)	1.39 (1.22–1.57)	0.05 (−0.13–0.23)	−0.25 (−0.27 – −0.23)	0.33 (0.02–0.61)	1.74 (0.88–2.55)
Elapsed time	−1.38 (−3.22–0.50)	−1.03 (−1.50 – −0.56)	0.00 (−0.08–0.09)	−0.05 (−0.13–0.04)	0.00 (−0.01–0.01)	0.01 (−0.12–0.15)	0.92 (0.52–1.31)
Citizen use	−1.24 (−6.11–3.82)	−0.59 (−1.71–0.58)	−0.37 (−0.58 – −0.16)	−0.08 (−0.30–0.12)	0.00 (−0.02–0.03)	−0.05 (−0.39–0.29)	−2.05 (−3.03 – −1.14)

Figure 6. Visualized path analysis of the driving factors of ecosystem functions. The relationship between driving factors and ecosystem functions that do not include zero in the 95% credible interval is indicated by arrows. At the start of the arrow, the positive and negative directions of the coefficients are described, and on the line, the values of the coefficients are described. The arrows of the FNS and GCA to carbon storage are excluded because the carbon storage of FNS and GCA includes not only ecosystem functions but also manufacturing processes